Supa Quick Robs & Swears customer

I was totally disgusted by the manner I was treated by the manager of this store. I called Supa Quick in Vereeniging to find out the price of tyres for my vehicle. The lady Lebo confirmed a price and I double checked if the price was correct. I arrived to fit on the tyres. Both the owner and Lebo stood together whilst they printed the invoice. I then paid the full amount as per the invoice. They removed my tyres even broke my tyre sensors and fitted the new tyres. Just before they could start the balancing of the tyres, the Manager called me and told me they made a mistake and that I needed to pay R6000 additional to the R9000 that I have already paid. I refused to do so, as it was a mistake on their side. However we felt sorry for the lady Lebo as she was so afraid. I couldn't understand her fear at that time. But we agreed that we will try and assist her. We traveled to Durban and unfortunately had a puncture and went to Supa quick in Overport, only to find out that they sold us the exact same tyre as the Vereeniging branck but way cheaper. Not only did they rob us, the manager had a dam nerve to call me and swear me names such as "F" ing " B". He is now demanding me to pay R6000. He swore the lady Lebo that works there accusing her of being drunk whilst I was on the phone. As for the owner he got so upset with us and started swearing his staff and shouting above his voice. It was the worst experience ever. I have recordings of this man swearing me over the phone. This was an error on their side and maybe if they didn't rob me and be more decent I would of considered paying them monthly, but to be treated so rudely. He was on speaker phone and my children had to hear him swear me in such a manner. According to Lebo the manager himself is suffering from addiction problems. Surely Supa quick being a company that claims to be of good standing, do random check ups and screening of staff. Very, very upsetting and painful to deal with. We are decent people. We dont talk harshly to people. I dont see why we should go through this.