Bad customer service

I have been with tracker for almost 2 years now, I sold 1 of my cars on the 5th February and on the 6th I phoned tracker for unit transfer and I spoke to Xoli and she told me I was going to be charged R1100 for transferring the unit and I was not happy with that and she referred me to the sales department and she had already briefed the sales lady of my complain and the lady gave me a 50% reduction (R550). I phoned again on the 10th February to take the offer and I spoke to Kgomotso / Sipho and we agreed on R550 installation fee and he arranged installation for the 12th and the installation went well. On the 13th I received the invoice with the R1100 installation fee and I immediately made a phone call and I was told that Kgomotso / Sipho will call me. Today it’s the 18th and I have not received any call from them or the new invoice of R550