Yes you can do it. The T-mobile USA network uses the same network footprint as AT&T (GSM) butt there is a chance of your phone blocks the sim card by inserting it and if it is blocked its going to ask you for a code.
Unfortunately I don't need a code.
An AT&T sim card will not work in an T-Mobile phone as it is locked to particular carrier itself... If you want to put your AT&T sim in your T-Mobile phone you can try unlocking your phone
Yes as long as the phone is att and has a sim card slot
No. The sim card would not be inter-carrier compatible.
Yes, provided your ATT phone is SIM unlocked.
Some cell phones are controlled with a SIM card. You may want to see if your AT&T SIM card will work a T-MOBILE phone.
Yes, provided your ATT phone is SIM unlocked.
The sim card will only work in a different phone if the phone is ulocked, in not, no
Could I put a simple mobile sin card to my HTC from ATT
if the phone is a prepaid phone, no. if it came on a plan, or bought outright, yes
YES, you can. IF you have an unlocked code for your at&t phone with T-mobile service. If you don't have an unlocked code, go to your local at&t store and they will unlock it for you, And, you won't lose any information with your T-mobile plan when you put your T-mobile Sim card on your at&t phone.
yes, but i wouldn't do that. It should work on any phone including t-mobile and att
yes u can I had my att go phone unlocked and tried to use my sim card from st. talk which I found out uses att service towers in my area however, it didn't work. It stated "sim crash"