A very dissapointed customer

I bought a set of pots from AMC in Durban, I paid cash as Khanyi the sales rep convinced me too. She went to the extent of taking me to the AMC office in Westville so that I could make payment as the credit card I used was not with me, I was treated like a golden customer. I came back home to Johannesburg and realised it was foolish to put it on credit, so I decided to call Khanyi and take the pots on laybye. The new contract was drawn up, AMC retained R1500 and put the rest back on into the account, the problem is that Khanyi is now charging me R3000 more for the pots, when I was told about the laybe option it was just R500 more than what I paid. Khanyi has still not gotten back to me on this matter. It is now October this deal was done in JuLY. I did not cancel my order, I simply changed the payment option, I do not deserve this treatment. When I was a cash customer I was treated very well, now that I changed the payment option I get treated like this, I am very dissapointed with AMC and want to cancel my deal completely. This is not fair treatment, a very upset customer.