Airtel — closing of my prepaid sim number

Address:

Chennai, Tamil Nadu

i have taken the pre paid Sim Number is [protected].But,i had paid ~ rs.3299/-- paid for 2 months which is not having any details of phone calls by me.Due to sudden increase of pay bill i have decided to close prepaid and buy post paid Sim.
So, i had 2 to 3 times went to airtel show room in porur and said about the closing of my airtel number and taking the post paid Sim. they told that net not functioning and here it is not possible to do.and also finally amount settled.Now I bought a new post paid Sim seperately.But without using last ~45 days,suddenly one of subscriber called and asked for bill payment of rs.760/--.for the pre-paid Number.
It is really hurting to me.

KINDLY INTERFERE THESE ISSUE AND SOLVE.

Regards..,
A.Gopi
[protected]