Bad service from Renault Kempton park

I bought a car in December and the disk of my vehicle was not changed and it is still registered under Renault Kemptonpark , other than the other issues I had after purchasing this car, the guy who was helping me got fired and I have been in contact with about 05 people including the department manager who isn't very helpful either, the one keeps on blaming the other and I have told them this is none of my problems because they now got their sale so they don't care about me anymore. I had to fight for even a silly gift. Please help me as I no longer have a strength to fight with people, at one stage the one guy told me that this is not his department, I told him that he represent the Renault brand irrespective of his department.