Bad service resulting to car damage

I went to Sasol Maitland on the 28th Feb and as part of the service, requested that oil be poured into my car. The attendant did not put back the lid after pouring the oil and as a result my engine is filled with oil with possible damage to my car. I've requested to see the manager and was told that the manager has already knocked off. I then left my contact details with the only copy of the card payment that I had so that they can do a thorough investigation before calling me. It is a week after I first reported the incident and there has not been any feedback. I've tried calling them but they keep telling me that the manager is not available.

I cannot drive around in a car that smells like burning oil and possibly damaging it any further due to Sasol's negligence.