denying work done on repairs

Bought a VW POLO at VW NTT PAARL Nov 2014,after signing all my papers i was told there is a knocking sound they need to fix,in Jan 2015 they fixed the noise,now 7 months later i get a cv joint noise coming from the car,take it to Barons N1 city and they discover the left cv boot which Paarl replaced was'nt clamped which now caused my cv joints to be damaged.Phone NTT PAARL to let them know and get an order form for N1 to fix it,now NTT PAARL is denying they replaced the boot even though we sent them the invoice and photos showing a list of repairs they did in Jan.So why give a 1 year warrantyon your workmanship and when you have to make good on the warranty then you looking for excuses.We tried to get hold of the managers but they never available and refused to pay to have the car fixed.I am looking at R6000 worth of damage due to neglegence from there workmanship.