D. Thomas Jewelry Inc

I have a written contract with D. Thomas Jewelry to sell my ring and he has violated terms of contract.
I have a contract with D. Thomas Jewelry to sell an engagement ring for me; one ladies diamond engagement ring. Center is a round brilliant ideal cut measures 7.69 x 7.66 x 4.82mm weighing 1.83cttw, 56% table, 62.9% depth. Clarity enhanced si-2 and f in color. Set into a four prong setting. There is four round brilliant cut diamonds on each side of center .41cts clarity si-1 and g in color. The terms of the written contact state that, once the ring is sold, I would receive payment in 30 days. Mr. Thomas indicated to me that the ring was sold and I would receive payment in approximately 3 weeks. Repeated phone conversations with Mr. Thomas in an attempt to collect the monies owed to me were unsuccessful. Mr. Thomas claims that he is waiting for something to clear at the bank and the person he sold the ring to, had given him a postdated check without him be aware of it. Mr. Thomas also indicated that he already received $2,000 out of the $3,040 due for the ring. The terms of the contract do not state that Mr. Thomas must receive full payment from the buyer prior to me getting paid. Mr. Thomas continues to ignore repeated phone calls and attempts to collect payment.