Airtel — porting request rejected

I recently applied for porting of my number [protected], but it got rejected on he basis that my connection is less than 90 days old. I recently converted from postpaid to prepaid, but my association with Airtel on same number has been for more than 3 years. This seems to be a violation of TRAI guidelines as my other colleagues were successfully able to port out with similar situation. I contacted nodal office but they didn't help in resolving the issue.