Paying for the return job

On the 26th of October I took a car Polo Vivo for them to fit CV joints on the 9th when I was driving the car it just stopped on the road in the night. I phoned them reporting the matter the following day ,they came and took the car apparently the mechanic who was doing the car forgot to tighten the *****s, hence it stopped on the road. I felt I was ********** because I paid the first time and for the return job they also charged me. They made the mistake when required to fix their problem they charging for the return job.