Airtel — My Number [protected] is Inactive, Now AIRTEL is asking to pay 25K to buy it again

Address:

Vastral Ahmedabad

I bought my Airtel Postpaid- [protected] in 2012. I was using it till 2019.
But in 2019 i could not pay the bill so Airtel inactivated my number.
Now few days I went to AIRTEL Store to resolve this issue and take it my number activate again.
They took some documents and assured me that it will be activated.
But later evening they told me that it will activated only if i pay 25, 000/- for the number as it is diamond category number.
My question is Why i will pay if I already bought it in 2012.
Please resolve the issue.