It appears this can be done on most phones, however can be quite technical. The basic user of a mobile phone is unlikely to manage this successfully without assistance.
You may get an AT&T universal credit card from a variety of sources such as the website universalcard or you may use the official AT&T website. Alternatively you can use the website known as citi.
If the Galaxy handset has been unlocked - yes.
No. The sim card would not be inter-carrier compatible.
if it's unlocked I think so, if not, procedures all over internet
If your phone plan includes mobile to mobile calling it does. If you're using prepaid it generally won't unless your on the $1 a day mobile to mobile plan.
yes, but i wouldn't do that. It should work on any phone including t-mobile and att
Absolutely, I do. ... Yea, but only if you buy it unlocked
Yes, provided your ATT phone is SIM unlocked.
Virgin Mobile now uses sim cards and ATT and other carriers only what customers to use their phones, so the phones are locked for use only on their network. If you get an unlocked cell phone you can use it on any carrier that uses sim cards. NOTE: Tmobile and prepaid carriers don't have Iphones on the service.
maybe if u unlock it...MAYBE
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.
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"