Yes, remove the SIM, once a ST SIM has been assigned a number it cannot be changed. Also go to your account online and remove the phone from your account so it is no longer associated with you. Explain to the buyer that they will need to create a Straight Talk account, add the phone to their account, and request a new SIM card from Straight Talk for the phone. They will send the new SIM for free.
Unless things have changed. That is a ST sold phone. If you remove the sim and sell the phone, the next person who tries to use the phone will end up getting your sim deactivated.
Thats how it use to work. With their new ST sim system this may no longer be a issue. But I wanted to get that out.
There have been report where people bought the E71 activated the sim and put it in another phone, then sold the E71. When the new owner got the phone and tried to get a new sim for it, ST would shut the sim off.
This is why people who want to sell their Nokias to get some money back are encouraged to buy a new ST/SIM and activate it and put the sim for their Nokias back in the phone and sell the phone whole. So that somewhere down the road their phone does not get shut down because the new owner is trying for a sim.
I do have a new SIM for my new phone. I bought a Samsung Infuse and ordered the SIM from ST for it.
So right now the SIM in the Nokia is the one that came with it from ST.
I did a total factory reset of the phone and removed it from my account.
I guess I will sell it without the SIM though just to be safe.
It sounds like you did everything right then. It sounds like if you have put the original sim back in the phone and done a factory reset on the phone while removing the phone from your acct you should be good.