Poor customer service from the best or nothing gang

Took my car (Mercedes Benz C-Class) for repairs at Bradburys in Polokwane 3 to 4 Months ago. The repairer ordered the parts needed for repairs at Mercedes Benz SA immediately thereafter. The repairer was informed that they don't have the parts in SA and they will order it in Germany. To this day, the parts (which are paid for) haven't arrived in South Africa and there is no ETA as well. Meanwhile, I am paying monthly instalment without fail. Repairer gave me the numbers of Mercedes Benz agent responsible for ordering the parts by the name of Tiaan Engelbrecht and he keeps promising to be getting back to me if and when he picks up his phone. I am very disappointed in Mercedes Benz SA for treating their paying customers like this. My financing contract will be up this September and I was looking to upgrade the car to the new C-Class. I don't think I will be doing that anymore.