Completely Inefficient

We are a small retailer who purchase about R3k - R4k of beverages from ABI per week. We had over-ordered some stock in error and requested that the stock be returned. This process to date has taken 6 weeks. After 4 weeks we managed to get the stock uplifted. After 2 weeks ( we are now entering into our 3rd week) we still haven't received our credit note. Our acc rep is completely useless. Her manager is no better. I have tried to contact the managers manager and no luck. I spent 17 mins holding at the call centre trying to get the Managers contact details. In 2 1/2 years we have not had one visit from a rep to see if we need anything, how the fridges are running. There is no client service. I have logged numerous requests on the in-house portal, called on the call centre number, sms'd and phoned the relevant people. This is unacceptable. I am now withholding acc payment in desperation so that I can get a R 700 credit. I would just like some service please.