I'm going to the UK soon and plan on using the pay as u go tmobile sim card in my USA tmobile phone.
Does anyone know if I can set this up BEfore i leave?
I put the sim in but since it isnt top upd im not sure if it works. I tried registering with mytmobile uk but they texted me the pin but I never got it. and since i cant log in without my pin, i cant buy credit to top up.

SHould I just wait to try and make it work when i get to the uk? or get a diff sim card?

i have a tmobile razr, if that helps any.

also does anyone know if i'll be able to buy ringtones once i get this worked out?

Why ask here? Why not call T Mobile UK customer service where you will be more likely to get correct answers.

Hi Peat
You should not have to register your UK sim, just pop it in and it should pickup whomever T-Mobile partners with here in the US (I would assume T-Mobile USA) To test it, go into the menu, you should see an option to top-up, dial that option if you want to test the sim.
As to topping up here so you have credit before you leave, if you do not have a UK address and UK credit card, i do not think it would be possible. Your best bet would be to see if you could find a top-up voucher on ebay or have a friend in the UK get a voucher an email you the numbers
I have a Virgin Mobile UK and an o2 UK PAYG sim i use when i travel to the UK, all I do is have a family member email me a voucher number, then I call the top-up line and enter the numbers and I am good to go before I travel.
A question for you, is your T-Mobile Razr unlocked? Just trying to see if your T-Mobile UK sim worked in a locked T-Mobile USA phone

If you have been a T-Mobile customer for 90 days T-Mobile will unlock your phone. This will allow you to use the T-Mobile UK SIM or any GSM SIM card you want.

I use a UK T-Mo prepay SIM in my T-Mo usa phones when I travel to the UK ( I had to get T-Mo USA to unlock the phone) The UK sim works fine here or in Canada ( although its a 2 step dialing process in canada which is weird, not that I would pay the .55 p/minute { zone 3 } to use it ) I top up the UK T-Mo account with Amex over the web as its the only foreign credit card they will take ( Beats me why ) or buy an extra top up card when I'm there.

hope this helps :-)

For the UK sim card to roam, it needs to have picked up domestic signal AND made a chargeable call, otherwise a brand new unopened sim card pack won't roam in the US.

Virgin UK sim cards do roam out of the box though. I have a bought a couple of brand new unopened virgin sims on ebay and they roamed here with GPRS activated too. And, you are correct...some of the UK carriers may require that a chargable call be made within the US. A colleague also bought an unactivated orange UK sim on ebay, activated it from here (by calling Orange customer service) and it roamed right away too with GPRS activated. At least Orange and Virgin are known exceptions

BTW according to the literature Virgin UK and Orange sim cards need 1 chargeable event every 180 days to remain active...but it is not necessary to make a roaming call to achieve this. Simply send a text message...that will be a chargeable event or if GPRS is active, go to www.polyphonicringtonez.com\wap and download a ring tone...costs something like 9p and will fill the bill!

hmm... i didnt know that good news i s'pose!

In Speaking with VM support, they told me the only thing needed to keep the card active is one chargable call every 365 days. I recieved an email from VM awhile back, here it is direct from VM
"Your Virgin SIM card will also stay active when you go home. All we ask is that one chargeable call is made a year so we know the SIM is still being used"
As to roaming, you can add o2 to Virgin and Orange, took mine right out of the pack, popped it in, registered on the website for the £5.00 free credit and it worked. I never really use the 02 since I prefer my VM account, it's been 6 months with no calls on the o2 sim, still have credit and the sim is still active