I do not trust in Maruti anymore

I had been servicing all my Maruti cars from Autocraft, Kolkata-700060 since 10 years. I trusted that any parts replacement made by them would be MGP. Over the years they consistently supplied spare parts from United Sales Agency, 7 Ganesh Ch Avenue, Kolkata-13 who I presumed to be authorised suppliers of MGP. The payments for these spares were taken in cash on bills raised by the local vendor. They follow this practice for all customers. They never gave me back the old spares or showed me the MGP packets. I learnt recently that United Sales Agency is not authorised MGP dealer. There is a clear unholy nexus between this service centre and the local dealer. I have been cheated like many other loyal Maruti customers. Maruti company lost their sales and reputation. I have all the evidences to prove this malpractice and unscrupulous activity of this service centre. Please investigate the service charges for fitting of spares and why on those particular dates no MGP spares were procured from authorised sales point. Can it always happen that customers buy spares from outside to be fitted in the particular service station? I have evidences to prove otherwise if they resort to this desperate excuse. I am deeply aggrieved and also hold Maruti responsible for letting this happen over the years.