Deposit R5000 forfeited

Dear Sir/Madam,I'm a customer of Auction nation since 2015 regular customer. I bought 4 cars on friday total R248,486.26 one of the car I didn't know I won the first car because my network was terrible. On Monday I went to the office to inform them if I will pay for 3 cars total R200401.62 because i didn't budget for four cars they said ok I should pay but doesn't guarantee if they'll not forfeit my deposit of R5000 accordingto the lady on the counter. I told them there's a room for negotiation in a any business as a regular customer. Finally I paid R200401 for the three cars to my surprise they forfeited my R5000 so I feel cheated and disappointed because I never did any cancelation. I tried sent many emails to the manager to no avail. I want Auction nation to reinstate my R5000. If they want to take any money it shouldn't be the whole money. Auction nation isn't fair to me as a customer I want them to them to refund my money and if I knew I wouldn't have paid for the three cars as they forfeited my R5000 deposit. So want Auction nation to pay me my money R5000. Kind regards, Nwaokpo.