Ouch. I've done this with 2 of my samsungs LOL the default unlock code for your phone and most is "12345" if u changed it, it should be resetable through are a hard reset BUT don't reset anything until u talk to the carrier u have, att, T-Mobile, Verizon, sprint they can 100% help u. It happens a lot lol. Usually right after u change it it happens. Just make sure when u do put a new code it right it down before u hit enter! If they can't help they'll refer u to the store u purchased it from. For me I just drove to Verizon right down the road from my house and they took care of it no problem..
Good luck gun hope this helped!!