Fantastically stupid cell phone question

[MrCoffee]

if i buy a cell phone on craigslist that is allegedly compatable with my carrier, will it work if i just swap the SIM card?

i don't want to do a thing that will cause the carrier to re-up my contract, but i don't know anything about cell phones except that i ran over MrsCoffee's with the car.

[irish.lambchop]

1. I hope it wasn't

on MrsCoffe's person at the time! :) Call your carrier - usually you can just replace the SIM card but it might be a different number - not sure.

[Kutjara]

2. There are three possibilities with cellphones.

First, a cellphone can be locked to a different carrier from the one you subscribe to. In that case, your SIM wouldn't work without an "unlock code" provided by the carrier the phone is locked to (NOT the carrier you subscribe to). They are reluctant to give these out to non-subscribers, so you'd be pretty much stuffed if you bought one of these phones.

Second, the phone may be locked to the same carrier as the one you have your subscription with. In that case, you would be able to use your SIM card in it with no problem, but wouldn't be able to use the SIM card from a different carrier.

Finally, and best of all, the phone may be unlocked. You can use any SIM card from any carrier in an unlocked phone. Personally, I always buy unlocked phones and haven't bought a new cellphone contract in nearly ten years.

[MrCoffee]

3. you are a very helpful person!

thank you! is there any way to tell if the phone's been unlocked?

[Kutjara]

4. The only way to tell is to stick a SIM card in it.

If it works, then the phone is unlocked (or is at least locked to the same network as the SIM). If it doesn't work and pops up a message asking for an unlock code, then it's a locked phone.

Companies like www.mobileplanet.com sell unlocked phones, but they're pretty expensive because the purchase cost isn't subsidized by a carrier.

Is it feasible to get together with the seller and see if the phone will work with your SIM? If not, it comes down to whether or not you trust the seller.

How have they described the phone in the ad? Did they call it "unlocked" or just say it works on a particular network? If they say "unlocked" I'd be a little skeptical, because not many people are willing to spend the money to buy an unlocked phone in the first place (only tech obsessives like me). If they say instead that it "works on T-Mobile" for example, I'd be inclined to believe them, for the simple reason that mentioning it's locked to a single network reduces the potential number of buyers, something an unscrupulous seller wouldn't want to do.