How to unlock unactivated iphone 4?

Bought my new iphone off ebay. Here's the summary: it's unactivated which means I have no access to the menu, I don't know what the original carrier was or even what country it's from. The seller is not helpful too. There is no original sim tray because it originally had a gevey sim. How to find the IMES number so I can unlock this, if I can't even get past the activation page? The box says AT&T but it doesn't work with an AT&T sim.

Go to apple.com

Hi

i you do not know your iPhone original carrier,
please on your iPhone its show connect cable with itune and also the symbol of (? ) just touch the symbols its show your iPhone IMEI.
then contact the attphoneunlockingshop.us submit your order to check network they will provide your network
if you want to activated or unlock just fill out the contact us form they will provide you best customer support

To know the network to which your Iphone4 is locked you can use the site http://www.onlinegsmunlock.com/apple-iphone-4/rs16wp9/ contact the customer care of this site and tell about your problem. Here they are providing Network lock info service you can pay few dollars and get that service.using this service you can know the network name to which your iphone4 locked. After knowing the network name you can also unlock your iPhone4 from the same site using remote unlocking service provided by them. You don't need to have the original sim card to unlock your iPhone4 just you can easily unlock it using your non accepted sim in it.