Cumberland Heating

I had an air-conditioner installed in May. On payment (by cheque) the installer (also the owner) told me he left my receipt and warranty back at the office and would drop it by. Having dealt with Cumberland numerous times I had no reason to believe there would be an issue. I have called them every month since then requesting a copy of my invoice and warranty, and followed up recently with a letter, and so far I have had no response from them. Now I am worried that the unit installed was used or reconditioned, I have nothing to prove it was new, nothing to prove it is under warranty, nothing to prove I received what I paid for. I am only asking for my receipt and cannot understand why a company would not provide one.