Service complaint

I have purchased Tatasky set for my company guest house 3 months back, from past one month the set top box is not working, I made a complaint to costomer care and they told to resolve the issue in 48 hrs, till the date the problem is as it is and I’m loosing the subscription charges every day. Once the service engineer also visited the place and told us that he will replace the STB in 2-3 days, after that I’ve received several phone calls from the Tatasky but they are giving me excuses every time.
Kindly help.