Airtel — excess of daily subscription deducted violating their own terms in respect to customer id [protected]

Sir,
We have airtel Dth connection, customer id no [protected] in name of Anita valecha (Mob No [protected])at our residence. We have two TVs in our home and both are arranged with setup boxes. Out of which the second number TV is not in operation for quite a long time and we are using only the first TV Dth service and are also paying regular monthly subscription for one base number @299/pm. Last such monthly subscription of Rs 299 for the month of March 2018 is paid by us as per demand issued by your message received on 24th March 2018 and same confirmed by us by your customer care executive on 24th march itself.We have clearly intimated them to use only one base connection. They suggested us to pay exactly 299 (neither less nor more) and we followed. We got a message too from airtel (AD-AIRDTH) on 24th March confirming the amount they received along with a remark intimating us for next due date 25 April 2018.
Now today I am getting a message from airtel to pay further amount immediately to continue my service. I am unable to understand how they can demand violating their term of one month. I tried to contact the customer care number today many time to register my grievance, but they are not replying and disconnecting my call. Please help me and instruct your division to provide me service till 24th April 2018 as per their term of service.