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Thread: iPhone 5, orphaned but still kicking

  1. #31
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    Why would they need to care if the pairing changed from before for TracFone usage? If it did change, what are they going to do?

    Each connection to the network should be independent of the past connections as far as I can imagine. Both the SIM and the IMEI have to be clear for operating on the network, but they could be independently checked.

    Quote Originally Posted by rchang View Post
    There is no evidence that VZW stores the balance based on IMEI. The whole point of a SIM card is device Independence. VZW supports SIM swapping for their own customers, so it's hard to imagine that they use a separate system for MVNO customers.

    I swapped a VZW SIM this morning, while it is plausible that Verizon went and looked up the account info when it noticed a different IMEI using that SIM card, that is so much more complicated.

    BTW, when I swapped the VZW card out of my Moto G5, I also swapped in an AT&T SIM into the G5. So, VZW doesn't even own the IMEI anymore. AFAIK, the phone only has one IMEI. Next time, I'll turn on the phone with the AT&T SIM first. Then, it will be clearer that AT&T already told Verizon "Hey, the phone with this IMEI is on our network now." Don't see how VZW is going to store the balance by IMEI in that situation.

    My understanding is that every time you turn on your phone, or even when you reconnect to the network, the phone companies have to recheck the IMEI-SIM pairing to see if it has changed from before. The SIM card says which account to charge, the IMEI says which phone is being used.

  2. #32
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    Quote Originally Posted by BassClef View Post
    About how long does an iPhone stay usable and safe to run after it can no longer support the latest OS? I believe there are people on here who are still running an iPhone 4 or 4s on Tracfone, right?
    iPhone 4S on the $3 T Mobile plan. I am having no problems with the iPhone 4S which is in mint condition.

  3. #33
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    Quote Originally Posted by tfusr19 View Post
    Why would they need to care if the pairing changed from before for TracFone usage? If it did change, what are they going to do?

    Each connection to the network should be independent of the past connections as far as I can imagine. Both the SIM and the IMEI have to be clear for operating on the network, but they could be independently checked.
    Assuming that the logic goes

    If SIM IMEI pairing same as before

    Charge to same account

    else

    Determine if SIM card number is valid and go get balance info from TF or whoever owns this SIM

    If looking up account info is really quick, then you can do it every time. Otherwise, it would be faster to retrieve that info only when there's a change.

    Also, you can SIM swap TF and non-TF SIMs. So, the phone company can't assume that phone is always being used with TF.

  4. #34
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    Quote Originally Posted by rchang View Post
    Next time, I'll turn on the phone with the AT&T SIM first. Then, it will be clearer that AT&T already told Verizon "Hey, the phone with this IMEI is on our network now." Don't see how VZW is going to store the balance by IMEI in that situation.
    I don't think AT&T needs to tell Verizon that the phone is now on AT&T network. When you put in an AT&T SIM, the phone will connect only to AT&T network (or a roaming partner if allowed). As far as Verizon knows, that phone IMEI is offline on their system. While I'm not certain that Verizon stores the balance based on IMEI, your example does not preclude them from doing so. If that IMEI is being used on AT&T with an AT&T SIM (a different account), there is no reason for Verizon to muck with the balance of that IMEI on their system which is under a different SIM/phone number/account.

  5. #35
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    How can balances be stored based on IMEI when you know SIM swapping works? How were you able to make a call with your E4 with a previously activated TracFone CDMA SIM when Verizon has no IMEI registration for it?

    Quote Originally Posted by hpham View Post
    I don't think AT&T needs to tell Verizon that the phone is now on AT&T network. When you put in an AT&T SIM, the phone will connect only to AT&T network (or a roaming partner if allowed). As far as Verizon knows, that phone IMEI is offline on their system. While I'm not certain that Verizon stores the balance based on IMEI, your example does not preclude them from doing so. If that IMEI is being used on AT&T with an AT&T SIM (a different account), there is no reason for Verizon to muck with the balance of that IMEI on their system which is under a different SIM/phone number/account.

  6. #36
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    Quote Originally Posted by tfusr19 View Post
    How can balances be stored based on IMEI when you know SIM swapping works? How were you able to make a call with your E4 with a previously activated TracFone CDMA SIM when Verizon has no IMEI registration for it?
    You have a point.

  7. #37
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    I'm glad it sunk in the second time

    Quote Originally Posted by hpham View Post
    You have a point.

  8. #38
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    Quote Originally Posted by tfusr19 View Post
    I'm glad it sunk in the second time
    Missed your post the 1st time. Was concentrating on answering rchang's post.

  9. #39
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    Independent of what has happened in the past
    1. IMEI is either allowed or not for the carrier
    2. SIM is either valid or not for the carrier.

    I could use a IMEI 1 with SIM 1, then IMEI 2 with SIM 1, then IMEI 1 with SIM 1.

    What is your query logic for this, assuming I used ttd each time before swapping SIM/phone?

    They don't even have to check the account balance until I try to use either of ttd.

    TracFone and carrier could push changes to each other and stay in sync with updates only happening if ttd is used or airtime refills are added to the account.

    I still don't see any reason to recalling past IMEI/SIM pairing data for normal phone usage. Let's assume pairing and ttd history is stored, but recalled only for law enforcement purposes as necessary.

    Quote Originally Posted by rchang View Post
    Assuming that the logic goes

    If SIM IMEI pairing same as before

    Charge to same account

    else

    Determine if SIM card number is valid and go get balance info from TF or whoever owns this SIM

    If looking up account info is really quick, then you can do it every time. Otherwise, it would be faster to retrieve that info only when there's a change.

    Also, you can SIM swap TF and non-TF SIMs. So, the phone company can't assume that phone is always being used with TF.

  10. #40
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    I don't think we are disagreeing about anything here.

    Caching is a standard strategy. I don't know for sure that they are caching, but it is likely. It might even be done in hardware. The number of times that your phone talks to the cell towers greatly exceeds the number of times you SIM swap.

    I'm not saying that they are looking up past IMEI-SIM pairings to find out anything about it. They need a really fast method to check if anything has changed. Even your $50 router at home does this. They quickly check the MAC address at each port to determine if you unplugged something and plugged in a different device. I doubt Verizon's tower is going to ping TF's database every time you send a text message.

    I'll ask my wife's cousin who used to work on hardware for cell towers next time I see him.

  11. #41
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    Quote Originally Posted by tfusr19 View Post
    How can balances be stored based on IMEI when you know SIM swapping works? How were you able to make a call with your E4 with a previously activated TracFone CDMA SIM when Verizon has no IMEI registration for it?
    I think we need to send one of us go find out how the hardware in cell towers use IMEI numbers. I always imagined that they work similar to MAC addresses for the internet.

  12. #42
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    Did some light reading. The communication between your phone and the cell tower is encrypted. When your phone first contacts the cell tower, an encryption key is selected. Further communication with the tower uses this key. Don't know how long this key stays valid, but during that time presumably they don't have to check that the IMEI and SIM are valid again.

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