Airtel — Refund for my Airtel Dth - [protected]

I took connection of airtel, dth and broadband, for dth connection the security deposit of 1500 was paid.
i was told that if I have active connection for 12 months of Rs 153 and this money will be refunded.
but after completing around 16 months of connection I submitted my set top box in good connection but not they are telling since you were in airtel black your active connection should be 360 and not 153, and they are not refunding the amount.

I also have a mail communication where they just mention 153 and not 360, also they asked my to submit set up box now they arr neither refunding the amount nor the set top box.
Request you to kindly look into it.