Car dealers are the same

I have lodged a complain with VW South Africa pertaining my car (POLO Vivo) which I bought at Dutton Motors last year june, I seem not to get any help from both companies. The problem with the car is the air-con which doesn't produce any cool air from last summer, also this problem wast discovered by the technicians at a car dealer when I took a car for 30k service interval and was advised to book a day for them to re-look at it and fix at no cost. Now for the mere fact that the car was bumped this year May on the right hand side of the the fender and was repaired now they claim that the warranty wont pay for the repairs of the air-con because a relay is not found (not there). They say maybe it was taken by the panel beater, but now how do I prove that their technician (car dealer) didn't take it either? Worse this fault was discovered long before I took a car for panel beating.