Bad Service

I serviced my car in April at GWM Newcastle branch, whilst visiting my parents. When I indicated to them that my speedometer doesn't work (it keeps dropping) I requested that they fix the problem. The lady who I was dealing with ensured me that she would arrange for GWM Midrand (as I live close by) to contact me as soon as they receive the part needed to fix the speedometer as the Newcastle branch didn't have the correct part. My car is still under warranty and the lady ensured me that the part's cost and installation fee would not be at my expense since the faulty speedometer was not at my fault. On numerous occasions I called the Newcastle branch to follow up as to why Midrand hasn't contacted me in this regard which she rep**** that she will get hold of them shortly. I am concerned that GWM is waiting for my car to run out of the warranty period before they contact me, which is the end of October 2015, so that I pay for the faulty speedometer. I am very dissatisfied and completely \put off"by the whole franchise as this is not the first problem I have with GWM! When I purchased the car I received the wrong spare key. They still haven't given me the correct key!!"""