Poor customer service

On Saturday the 10th of April I called the Supa Quick in Vosloorus to get a quote on tyres, I spoke to a guy named Thabo, he asked for the tyre size and I was quoted R850. I was happy because that was a good price since I had been shopping around, I told him I'd come to the shop on sunday morning to get the 2 tyres fitted. When I got to the shop I told them that I had spoke to Thabo the previous day, they fitted the tyres and asked to add a wheel alignment, to my surprise when I have to pay I'm told that each R1175, I told the owner that I was told it's R850 which he disputed. I stood for some time whilst they were trying to get hold hold of Thabo since he wasn't at work. I was asked what should they do now cause the tyres are already on my car? I was very upset as I didn't not have additional R600 that I had to pay, I ended up having to call a friend to send me s ewallet that I can get at the nearest FNB ATM to pay. This was a huge inconvenience. This is high level unprofessionalism. What I don't understand is where the R850 comes from cause I had given him the tyre size. The service I received is highly unacceptable, I didn't even get a simple apology from that Thabo guy when he eventually decided to show up, I just paid and left the premises and told myself I won't be returning for anything.