Shocking Service from the dealership

My vehicle was in for a service at the dealership last week Wednesday and collected my car the same day. Friday I drove my car and noticed that there was something wrong, the car was jerking and loosing power, I took my car back the Saturday and the technician took my car for a drive to see what the problem was, he returned saying that he noticed there is something wrong but he checked and cant find the fault. The technician advised it must be the petrol and that I should refuel with other petrol. Ive refuelled and my car still has the same problem. Hyundai phoned me to do a follow up which I notified the lady that my car still had a problem which she advised they will phone me back, no call back received. I phoned the dealership this morning again and was advised that I have to take the car back. My problem here is this is not the first time im having issues with this dealership, with my previous Hyundai I also had the same issue, took my car in for a service and two days later my car was towed in back to the dealership for them to fix what they messed up. After they fix my car now I will not go back to this dealership again!