Disappointed customer

So I went to Supa Quick in Bloemfontein in Zastron because I had a slow pucture. They took my car and did what they had to do. When I was going to pay, only then was I informed that my centre cap is missing, something they did not inform me prior to the service. They were kind enough to inform me that the only way this would come off is if the tyre had been taken off, which is exactly something that they had just done. So me being me, I first want to verify if the thing did not come off before going there and I do. The centre cap of my tyre was there before going to Supa Quick and just like that it is gone. I just called now and spoke to the guy handled my service who now gives me another reason why it would've came off, this is now after I told him that it was not missing when I drove there. I asked him why did they not show me before taking off my tyre that the centre wheel was missing, why did they only make me aware after they were done fixing my tyre. We take our cars to such places because we trust they will do the right thing for us and not ***** from us. I am still waiting for them to call me back to tell me to come get my centre wheel cap. I am truly disappointed in this service. Fixing the slow puncture was R140 but now i am expected to pay more to replace my centre wheel cap.