Poor customer service and incompetence.

I have had to return my vehicle to Volkswagen Hatfield Bryanston 5 times in the last 3 months to have an issue with the throttle resolved. The EPC light appears on the dashboard and the vehicle loses power. The first time I took my vehicle in, they charged me about R2000 to run "standard VW tests". The vehicle was returned to me. The following day the same issue occurred. I returned the car. The technician, Liam McKonky advised that he "adapted the throttle" so the issue should be resolved. The vehicle was performing ok for about a month. Then the issue occurred again. This time they tell me I have to replace the throttle with a brand new one which cost R7000. They replaced the throttle. A brand new part. The issue is not resolved. This time they put the old throttle back. They tested the car and said that it should be fixed. The issue is still re-occurring. I have tried speaking to the Dealer Principle Cheryl Claasen. She is unhelpful. I have spoken to the Service Manager as well. All he could say was he doesn't know. I am unable to drive the car or sell it. I purchased this vehicle, a Polo Comfortline 1.6, brand new in 2012 from this dealership. My service history is up to date and I have only ever taken it to VW Hatfield Bryanston for a service and any other issues. This is complete incompetence on this dealership's part. I have already paid for this to be fixed and I am still sitting with the problem.