Poor service by Paul Maher Ford-Beyers Naude

We are really disgusted by Paul Maher Ford's service, we took our car there to be checked on the 19th of June 2019 since it had a knocking and funny noise.They took the car and told us they wll call to tell us what the problem is.They then called my husband and told him that that car only needs service and a new engine mounting and it will be ready for collection the following day,we then gave them a go ahead. They then called us again to inform us that they have discovered that the problem was not the service only there might be a serious problem with the engine as a whole and we will have to pay R8500 for them to strip and diagnose the problem further and also pay for the servicing of the car and engine mounting on top of that. They then sent us a quote of R57000 for repairing the engine. So technically we are expected to pay for the service and engine mounting done, plus diagnosis of the problem and repairs on the engine.Were they not supposed to diagnose the problem of the car in the first place and give us give us a full quote? Instead of making a guess work? When one does not come out right they try something else and if its also not working they try the other..We are expecting it to be an accredited ford dealer that carries out their services with great integrity.