I have a signed contract with my signature, 2 witness signatures, and the signatures of 2 people, who, in the contract, agree that they owe me money.

 I do not practice in Oklahoma, but I have handled cases in more than a dozen jurisdictions, and I don't know of any that require that a contract be notarized, although it might be necessary for prenuptial agreements, separation agreements, etc.  Some documents, like deeds and wills, neither of which is a contract, require more formalities, but witnesses are generally enough.  Many contracts are not even required to be in writing.  Again, I don't specifically know about Oklahoma, but I'd be surprised if notarization was required.