Bad customer service

I bought 10 buckets of rubber sealant and 2 bonding liquid from this shop and one of the buckets was almost half. I took a picture and sent it on WhatsApp and didn't get a response the whole day.

Today I sent another message. The guy who was speaking to me on WhatsApp was very rude. He told me to relax, that I'm not the only customer, and he was dropping my calls. He asked me if I have used the paint, I said yes we have used the paint. He said according to him the buckets are filled accordingly from their factory, then he said someone can lie that the paint was not full.

What would be my point of lying when I bought so much paint? I also told him I have been a customer for more than 5 years. He said being a customer doesn't give me entitlement to ask for another 5L when the bucket was not full. Instead of apologising, he continued being rude to me.

We had another quote for R19,600 from them and I have cancelled it. I'm not going to be buying from this shop anymore.