Airtel — Conversion of the prepaid mobile number to postpaid number

Sir
I am using the mobile no [protected] with airtel network for the last so many years,

On 3 july the company converted my no from prepaid to postpaid without my consent and notice.

When i approached them they donot give any reason of the confirmation.

Also the recharge done by my side has been closed by the company.

They have activated the plan of rs 1000 + gst on the number

Now they are not allowing me for the the porting of my number because of the outstanding