Boondock Builders

when I initially sent my estimate to the customer, despite my prices being very reasonable, they said it was more than they could afford. The customer is elderly and so, trying to be compassionate, I lowered my price significantly, by about 40%. The customer said they wanted to use PT 2x6 lumber for the deck and I suggested using actual decking planks because PT isn't really intended for a finished surface application like that. I told them I would be concerned about splinters and such potentially. they said that because of cost they wanted to get it made out of the PT. as one might expect some of the wood had a little bow but I corrected that when I installed by using spacers to make sure everything was even and straight. there were a couple knots and the homeowner, who hovered around the entire time we were working, asked for a piece to be flipped over which we did. at the time they made no complaints about the quality of the material. I gave them an invoice which included the cost of material and I showed them on a home Depot receipt that I was not charging them anything additional for the lumber. subsequently they tried to file some sort of claim they say with home Depot because of the quality of the material. home Depot told them that the receipt I gave them was not a valid receipt? I don't even know what that means. how is a receipt invalid? they contacted me asking for a valid receipt and I did not know what to give them as they already had the receipt from the purchase of the lumber. on the day of the installation they had no complaints about the job or the material, aside from asking for one piece to be turned over. leaving a two-star review after I cut my price almost in half to try and help her out is pretty low in my opinion. All because of a receipt...