Airtel postpaid balance to bank possible !?

hi, I had Airtel postpaid. during this year starting, I wanted to get utilise MobiKwik supercash. so did recharge at all possible ways my sc get utilised. and postpaid bill went upto -8000.
I did all these, because I studied in dd, that on converting from postpaid to prepaid, the Balance amount will be given back to bank account.
and I too converted to prepaid. at that time they told they will send to my bank account and got details. in September.
they didn’t send in given interval, so mailed them, and asked to send blank cheque, also sent it.
still they didn’t send.
mailed them last week. got call today and they are saying, they can’t transfer balance to bank account….
“as I did those payments in little by little like 10 20 30 50 to get cashbacks from other sites, so they won’t transfer to bank”.
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totally rubbish, ya I accept I did like that to gain offers, and mostly sc consumption did with 500 and all….
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any help ….. ??
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if they won’t transfer, and gives only as phone balance, can I do recharges for other Airtel numbers, with that balance from that number ????