Care Rehab Claiming they never recieved my payment via Credit Card and then trying to double charge me. Internet

I purchased a "Tens" Unit from a local rep for muscle therapy. My med insurance was promptly billed and they paid their portion. That left me with a bill for around $150. I paid the invoice within the month around May 09. In Nov 09, I get sent another bill for the same amount. I call them up and they claim they have never received a payment from me and that I have to send them proof that it was paid many months ago.

Luckily I had the account statement handy or I am sure I would of had to pay for it again as there was nothing they could do for me without proof.

I am still in the process of submitting this paperwork and hope it turns out ok. Becareful with them as it appears to be YOUR responsibility to prove to them you have paid.