Samsung mobile india - Delayed Service and not provided bill for amount paid

I had given my mobile for screen replacement at Ratna Electronics (Samsung Authorized Dealer) in Hyderbad o **st March. It took ** days for repair, no one had even updated me on the repair status even after multiple follow-up. Then after ** days they asked me to come and collect the device. I had paid **** and they handed over my device, it now I did not get my bill. I am continously following up to Service Centre and also in mail to Samsung CEO desk and also in social media like (FB and Twitter) but no one is responding. As a customer it is my right to provide me the bill on my name for the amount I paid, which I didn't get. Looking at the poor response I doubt the genuinity of part replaced in my device and also the personal data privacy in the mobile during the period of service.