Airtel DTH - Money not refund by company

I have four Airtel Dth TV connections at home. There is a rule of less amount on all child connections. From the month of Jan ****, Airtel is deducting the full basic amount of Rs.***/- on every connection. I called up customer service to reduce the amount but they always refused this by saying that there is no rule of less amount on child connections. But I saw an advertisement page on airtel Dth that if you are having multiple connections Rs.**/- basic amount to pay instead of Rs.***/- on all secondary/child connections. I called up again Airtel customer care on ** May **** and lodged a complaint about this issue vide complaint reference no. ********. Then I got a call from Airtel and they agree on the overcharge for the last * months. But they refused to adjust the overcharged amount. They only refund one month amount in my airtel account. Rs.***/-. I need all amount which I had paid and it must be adjusted in my Airtel dish account. Airtel team senior executive disconnected my phone by saying not possible every time. Can we take a call on them for this kind of poor service and my mental harassment and time wasting? Please help if possible.