Airtel — signals

My no is 97790463 — . My problem is i ported my no last month to airtel post paid, they issued me the sim card and activated it but there were no signals or very very weak signals. After confirming the sim faulty they changed the sim but the problem was same. After being visited personally n having made several complaints on customer care centers the problem has yet not been resolved. Even one of airtel service engineer visited my place n agreed the problems being created from airtel side.
As got checked from the server, by one of the customer support executives, my usage was negligible thats only because of poor / no signals. Pl resolve my problem by earliest.

And after all this the airtel has issued me the bill. Pl tell for what do i pay to airtel if they have not provided me any services.