[Resolved]  Tata Sky — company technician not informing about charges (rs 400) after replacing set top box, tata sky reducing the subscription days

Tata sky technician visited my house on complaint of no proper picture (Continously picture rolling and no picture) he replaced the set top box saying that the tv was getting low signal. Evev after replacement of the box the same complaint existed and was informed by the technician that was fault in the tv which was later repaired by a tv technician..
Why was the set top box replaced..?
Why i was not informed about the charges?
How can tata sky deduct rs. 400/=from my subscription charges by just sending one sms about charges.
How can "tata sky" reduce the number of days from my subscription period (28 days =1month)??