Airtel — Charging for replacement of STB that is Airtel Property

Address: Pune, Maharashtra

My customer id. is [protected]
I am using this connecting for past 3 years and now due to some issue Airtel technician wants to replace it.
Airtel is expecting me to pay 350 Rs. for the replacement.
If Airtel owns the STB and I have paid upfront for the set-top box services then why am I asked to pay for this replacement? This is not acceptable since if I terminate the services then the STB will be returned to Airtel.

Need your immediate attention.