Individual Water Heater Installed in Attic Ripon, California

We had Roberto's install a water heater in our attic. He charged us a miscellaneous fee of $150.00 to do this. He did not need to replace any gas parts or hoses, due to those being new. He charged us parts and labor $1600.00.  total of $1705.00. We feel he really over charged us.  We haved called him a couple of times and he never responds. 

He has yet to give us an itemized receipt so we can register this water heater for the warranty.  My only thought to this is there was possibly a rebate on the water heater and he may have kept the receipt to do this. I just spoke with him before this report and he said, the water heater was put onto a credit card and he cannot get a copy of the receipt.  I told him I am going to repot him to the BBB and file a smalls claims court action. He said, Really over a receipt. I said, Absolutley!