What were the terms? Was it a graduation gift? The uncle has to prove that loan. Did you keep the gift card? Memorabilia from your graduation? A picture of you and your uncle at that time? You need to immediately pull together the evidence that it was a loan.
Your uncle will have the burden of proving that this was a loan and only when he does so successfully will you have to rebut with proof of a gift. Your uncle will also have to prove the amount. Oral agreements are enforceable in Florida, subject to certain affirmative defenses. You are able to ask the lawyer for proof, but you are also able to discuss the issue with your uncle and try to come to some sort of resolution without and before a lawsuit is filed.
This answer does not establish an attorney client relationship and is just my opinion based upon the limited facts presented.
Ironically, it may now be YOU that has a legal action against both the lawyer and your uncle. Unless my math is in error a "loan" of 800, with a repayment in 90 days, yields an interest rate in excess of 18% and is usurious. This would likely violate the FDCPA and the FCCPA and subject both of them to legal action where they would have to pay you $1,000.00, plus actual damages and attorney's fee you incur.
You do not need to prove anything to the lawyer. The letter is designed to scare you into paying or entering into negotiations. If there is no evidence one way or the other, the lawyer will likely back-out from representing your uncle after their attempt to rattle your cage has failed.
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