Poor workmanship

I went to get new tires in November last year. Being a woman I trust that the service I am getting is going to be the best as you guys are the experts. I kept hearing a funny noise, so I decided to go to the dealership to see what the problem is, they charged me R820 for a diagnostic test. Only to find out the nuts on the wheels weren't tightened properly. I don't get why I have to pay someone else to do the job that was supposed to be done at Supa quick kempton park, festival mall. I want a refund, else I will take this further as my life was put in danger. I could have ****ed other people on the road as well. I have all the receipts and proof of payments. This service is totally unacceptable... How can you be trusted???