What to do to get full refund

I payed 20K for an item sold by a  TX seller three months ago. The delivered item was in a very poor condition and with a wrong serial number. I did not accept the item. The seller refused to refund and claimed the serial number specified in the contract was a typo. He is now trying to sell me another item instead. I don't trust him anymore and wanted a full refund.

I don't live in TX.

What Should I do?