Poor customer service

Cashbuild Moratiwa Crossing said they're unable to exchange the paints bought at a different store(Groblersdal) without a till slip that I'm unable to find. They said I should go back to the store for them to track proof of purchase and there's nothing they can do to assist, instead was given the contact number of a divisional manager. I've bought building material of more than R50000.00 at the same store without any hesitation. I was gi😏