A quote for R3500 which ends up as R6150

I contacted Finn Autorepairs in Port Elizabeth for a quote for a major service. I was quoted a "ball park" figure of R3500 and an additional R1000 if brake pads needed replacement. I also had a problem with a warning light which came on and asked them to check into this. I was given the "ball park" figure as they "shop around to get best prices on spares". When I arrived at the service centre I was informed that an engine flush needed to be done at R300, which I agreed. I was also offered an aircon clean which I declined but was charged for anyway. I was called later that day (01/09/2017) and was told that they had to get the air filter and spark plugs from Volvo. No problem and I gave them the go-ahead. I collected the car and was presented with an invoice for R6156.46! It was also mentioned that they had :cleared" the warning light and there would be a cost involved if they couldn't repair. I was told (in writing) that it was due to a fault and that the throttle body need to be cleaned. I paid and left and within 15 returned with the same problem. The attitude of the lady (I believe it was Imelda) was that I should read the writing on the invoice. A "manager"came up to me and was extremely rude and I left in a huff. There were lies told as the spark plugs and air filter had been bought from Volvo the previous day already. This information I got from Volvo. Volvo also repaired my "throttle body" as it was found that it was a perished vacuum hose which they replaced free of charge. I made contact with Bosch as I was under the impression that they were Bosch agents (I was wrong) but got a call from Imelda asking what this was all about. I explained the whole thing and she told me that she would discuss this with her manager. Mark called me later and gave me the run-around as "this and that and blah blah blah" I am not a mechanic but had spoken to a master mechanic who looked at the invoice and was horrified. So I haven't had any joy for being charged nearly double of what I was quoted, even though my brake pads weren't replaced. I am just sick of being taken for a ride by those who should be delivering a good service.