My doctor owes me $2,000 for cosmetic services her office no longer provides- how do I collect?

My internist offered cosmetic services - I bought $4,000 package- she had falling out with woman she hired to perform procedures- I only used up 1/2 of packages- I keep asking for refund- doc says " I'll handle it. " but I have yet to see check? I have all documentation- even provided copies to doc and a letter to please refund. Even spoke to her brother who is her accountant- he said that part of her business is no more and they are sorry? I feel doc keeps blowing me off and has no intent of refunding my money? Also is there a statute of limitations on money owed? It's been years! Thanks!