Sai Service Station — charging money for amc covered car

I want to register a complaint regarding the worst service from sai service station at borivali east. I have purchased the maruti suzuki celerio from sai service andheri (East) at the time of purchase i was taken amc for 2 years and they are assured us all work is done within amc no extra cost will levied. I purchased my car in the month of august 2016 and my amc is valid till 19/08/2018. I gave my car maruti suzuki celerio to sai service borivali on 12/08/2018 at the time of giving the car they are assure me to doing all work under amc covered at the time of delivery they are telling amc is not valid. We are having amc receipt which is clearly mentioned the date till 19/08/2019. They are charged me around rs.7000/- for all work which is already covered in amc. I really want to complaint for this pathetic service of sai service borivali and andheri east. Kindly give some reply as early as possible.