Airtel - Amount paid for plan Upgrade But not activated

Been a customer of Airtel Broadband for the past ** years. Opted for an upgrade on my existing plan of *** to ***. I paid Rs **** for half-yearly advance rental as it saved me around ** percent of costs. Raised a request on May ** for the same. Also raised a new connection for my neighbor on the same day.
The new connection was done immediately the next day. But upon following my upgrade request on the customer portal ***, they said this would be sorted in ** hours.
A week went by and no one contacted me. Called them again and again on a weekly basis due to the requirement of my Work From Home job. They keep telling me the same answer " We are escalating this. This will be sorted out in ** hrs".
Now almost after ** days of raising the request , the plan is still not upgraded. I am tired after almost * to * times of following up. In fact I am doing their job of following up on requests.There is no proper justification for the payment of Rs **** done.
I understand the Covid-** situation. Clearly this is not about the shortage of technicians, as the new connection request was done immediately. The only relief is that they bill for the old plan till now.
Airtel keeps advertising of their customer care so proudly. But this is a worse handling for a customer of more than ** years.
I have paid for a service, that is still pending. I feel I am a victim of Airtel's marketing traps in making customers pay advance amount, and denying the intended service .