Insult and unfair traetment

I phoned Build-it in Kwamhlanga, As a place where i buy all my building material regularly to veriry the price 6.6 m IBR Roof sheeting since i bought some before. Nelson from Build-it gave me a price for R320 each. i have confirmed the amount with him we made an appointment that i will come pay. I did sent my wife there on monday, it came as a surprise when i have been told that the price increased.I have tried to speak to Ruan/ Ryan Manager for Build-it by honouring the price but he refused. I ended up paying R780 extra. When is the time to swipe that amount he instructed his cashier that Build-it is not accepting the card i am using. Of which that card is the one i have been using everytime when buying something at build-it. The experience and the insult from the Manager is unacceptable if he treats build-it customer like this. That is black pollulated area that means i am not the only customer who receive such treatment. If Build-it Head-office is not dealing with this matter fairly and equally.