I heard some imei check sites give out false info and instead link you to purchase an imei unlock from them after.
Dont fall for it and avoid such sites.
Sounds like they're pulling a scam.
This is correct. You cannot trust IMEI checking sites.
Your carrier should be able to check this if you ask their tech department, or if someone makes a case with their tech department. Although, the first time after this is done you need to restore your phone and use an original sim from when it was locked to unlock it. This the carrier cannot check if has been done. But you should see a ONE TIME ONLY message with congratulations, your phone is unlocked in iTunes (this will not come the recurring times you restore).
To check, its not always enough to check with a None standard sim card, some carriers piggy back on others, and a lot of times sim cards from these work on locked sim cards of the "father" company and vise versa. So you want to use a sim card that is from a company that has different reception coverage (this distinguishes the piggybacking companies next to always).
My tip for you, is to call in to the carrier your phone is locked at, tell them you have problems unlocking. And ask that they try to order an unlock once more, they might refuse cause they are stupid retards (sorry its sometimes a fact), tell them a telecom technician told you this might fix your problem (I'm an electronics technician that used to work in a telecom company so your not lying). If they use the newest method of ordering unlock at the apple server this should be next to instant. But ask them how long it will take before you should restore, if they say you can do it instantly still wait til after the call is done. If they say very soon, wait an hour, or what they tell you to wait (and an hour more).
When you restore, have the original sim ready (or a sim card from the original carrier, it might be complicated to use one that does not work, so use one that works). Remove any sim card from your phone, then restore (backup if you will first, i dont care). When it is done restoring, you can insert your original sim in the phone before it boots if you want to, or else you might have to reboot again. Now if you want to activate without iTunes, i suggest you have a wifi with working internet connection ready, if not, connect it to your iTunes on a computer with working internet (I suggest you do it on the phone, you might have problems doing this in itunes if the computer has ever jailbroken a iOS device, you wont probably have problems, but you want to be sure this time right?)
Success?