Replacing broken iPhone 3GS with phone from ebay or similar site

[lamaz46]

I've been using the 3GS for a little over a year and it's broken now.  I want to know if I can replace it with another 3GS or other iPhone bought on ebay with my current contract.  It would be cheaper for me to do that than use my early upgrade and sign a new contract.  What I want to know is if it's possible and what other charges might be associated with doing this.  Having had an iPhone, I already have a data and messaging plan so what else would be involved in making the switch to a replacement phone?  

[MR_SMiT]

You can use any AT&T phone that uses the same size SIM card as the 3GS, it will not affect your current contract with AT&T. But one thing I did not know about, I ordered a AT&T Motorola Atrix 4G ( HSPA+ ) smartphone from Amazon, I installed my SIM card from my 3GS to Atrix, the phone worked with calls, and data. But 3 days later, I got an email and text message from AT&T, that I would have to get a 4G Data plan from AT&T, so I got a 4G data plan. I never need to sign a new contract, only add this feature. Good luck. 

[iDrummer3]

Even if you get a phone with a different size SIM, you can go into an ATT store and they will give you a new SIM in whatever size you need and update their systems with the new phones IMEI. Phone will be working before you walk out the door. All free.

[Antony007]

I have my receipt from my replacement today and in total it came to £139. As I'm still within the 1st year and there is no water damage, obviously that charge was waived.