Question about Locked RazR

I just received a Razr V3 from my buddy who is with Cingular. I am with TMobile. From what I understood, the 2 were basically interchangable with SIM cards. Well, when i got the phone it asked for subsidy code. Me being an electronics "dummy", tried some random codes only to find the phone saying "contact service provider" after 3 tries. I guess I should have found these forums earlier So, do I contact my provider(TMobile), or, the provider that the phone came from(Cingular). Also, does the provider usually do whatever it is they do, for free? Or should I expect a charge. Any help would be greatly appreciated. Thanks

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If it was a cingular phone, then cingular can unlock it, but why would they do it for you? duh ..
You can take it to a local private dealer (not the "cingular or Tmobile' stores. They usually have the equipment to unlock phones and may charge something for it, maybe 20 bucks or something like that. They you can put your t-mobile sim card and everything will be fine.