Roof tiles

I bought 2600 roof tiles from cashbuild inanda and the builder only used about 2100. we have 450 to 500 tiles left, I called the hardware and I spoke to the manager as I wanted to send this tiles back and buy something esle with that money. The manager advised me that they can't take lot of tiles back atleast if it was 10 to 20 tiles they should help but as I said it about 500 they can't. I called other branches to find out because I had people that used cashbuild before and they never had problems when they returning things, when I called other cashbuild around kzn I was advised that the tiles can be returned no matter how many there are. Why cashbuild has different rules? Their services were excellent but I am really not happy with this one, if it a rule it need to comply in all cashbuild hardwares.