Any - provided the handset has been unlocked. The network your phone uses is determined by the SIM card..
You will need another AT&T cell phone are a compatible GSM cell phone.
No, Sprint uses CDMA technology and AT&T uses GSM technology. Plus, the phones are flashed to each carriers cell towers.
none
Nextag cell phone headphones can be used on any cell phone.
No, Alltel phones run off of CDMA and AT&T and T Mobile use GSM
Speak to your mobile phone retailer as you will need to get a Bluetooth headset that is compatible to your current cell phone.
You cannot "De-brand" a cell phone. You can however unlock a cell phone. if that cell phone's software and hardware are compatible with another provider's network, then that unlocked phone can be used with the other provider. Your best bet is to ask the prospective service provider if the software/hardware on the phone that you want to unlock is compatible with their network before investing in the phone
Call t-mobile and ask to get your phone unlocked. Then call at&t and ask to set up service with a SIM card instead of a phone. Easy.
There are a number of different cell phone models that are compatible with GSM or Global System for Mobile Communications. Some of those cell phones include Apple iPhones and Samsung Galaxy models.
Some popular T-Mobile phones consists of: Samsung Galaxy S: Vibrant, Samsung Nexus S, Blackberry, G2, HTC, & many other phones.
You need to check with your cell phone carrier and they will have ringtones compatible for your phone
There is the HTC phone from AT&T