Airtel — Unable to recharge after converting Airtel Sim from postpaid to prepaid

Address: Hyderabad, Andhra Pradesh, 800037

I have converted my Airtel number from postpaid to prepaid today. When I try to recharge error msg appears 'Please enter a valid Airtel number'.

I am getting incoming calls but since I am not able to recharge balance is 0. So I am not able to make any call or even use internet.

Please solve the issue.