Hathway — Broadband service not activated

Hi, I am from chennai (pammal) and I took a Hathway Broadband service in Pammal area. They asked me to pay the amount 1492 and I paid. They kept the modem in my home and not activated the service because due to covid i am out of station. But Suddenly their agent said they were not able to provide service and taking back the modem.
They sent an email to refund the full amount and take back the modem.
As per their email their agent came and took the modem and later saying they cannot refund the full amount. Only security deposit they can refund.

This is pure cheating the customer.
Thanks
Senthil