Hello! I currently have a cheap smartphone that I got through T-Mobile and I use their prepaid plan. I am now interested in buying a refurbished iPhone 5/5C/5S so I've been doing some research. Those I've asked have not agreed on much so I found this site after doing more research. It seems as though folks here are generally pretty knowledgeable so I figured I'd give it a shot. I've talked to T-Mobile and have had different answers depending on the Customer Service Rep. Here are the things I've learned that I believe are correct: 1. Since T-Mobile is a GSM carrier and I'm looking to get an iPhone 5/5C/5S, I will need to buy one that was originally carried by a GSM carrier (like AT&T). A refurbished 5/5C/5S originally made for a CDMA carrier (like Verizon) won't work 2. When the next iPhone comes out (likely in September), there will be no more updates for the iPhone 5. Not sure about the 5C or 5S 3. If buying refurbished from a third-party (eBay, Amazon, etc.), it will need to be unlocked 4. Even if I buy one that's unlocked, the owner has a certain amount of time to report it lost/stolen and the phone won't work if they make that report 5. I need a T-Mobile nano-SIM card (my current cheap phone uses a micro-SIM) After all that, I found a 5C on eBay for a reasonable price. The seller has it listed as "AT&T Unlocked for GSM Carriers (not for Pre-paid)." Now that confuses me. If a phone is unlocked, why would it not work for prepaid accounts? I asked the seller and the answer I received was basically that it won't. I'm sorry if this is a stupid question, but do I have something wrong? Does the seller? Why wouldn't an unlocked GSM carrier work for all - even prepaid carriers? Any help would be most appreciated!!! Thanks so much!