Tata Docomo — postpaid to prepaid (store locator in chennai tamil nadu)

I have requested to change my postpaid sim to prepaid, they have send me a mail to visit tata docomo brand store and give aadhar card photo copy.

I search their website to locate the store in tamilnadu, i was shocked there is no stores located in tamilnadu, i registered a feedback again regarding this but they are not responding properly, even i have called the customer care number and inquired about this they also not responding, they just put the call in mute and cut the call.

I tried to port my tata docomo postpaid number, port number genereted with that number i went to airtel show room and asked for prepaid, they told me that prepaid is not possible and postpaid is ported to only postpaid, (Is this true?)

Anybody please help me on this issue, as i was using my number for bank and other related things.