Williams hunt Roodepoort bad service.

I took my opel astra 1.6 t cosmo to Williams hunt Roodepoort about 2 weeks ago. I send it in because of a limp problem. They done a ecu test but could not find any problem. Later they phoned me that it is the air max sensor. I had to wait a further 4 days because part was odered from PE. When i got the car back it was worse than before. There is no problem with the sensor i tested it. And i can get the exact same part from a supplier for R859 let you start thinking of their business ethics. They said i must return the car. I returned it on Friday last week early that morning. By Monday at 14pm i phoned them because of no updates on my car. Spoke to Retha an se said thebmanager will phone me back se will inform him now. It's Thursday morning no call yet. On Tuesday i mailed there complains department at Unitrans. Precious mailed me back with a Ref no. Up to now no respond. This is unacceptable service from Unitrans and William hunt Roodepoort. I just read their reviews it not at all good reading. I thought if im in their situation after loosing the backing of GM motors you will be customer oriented but no. Recept for closing. Unhappy customer. Pls help.