Airtel — number changed after porting

Address:

Kanpur, Uttar Pradesh

I applied to port my number from docomo to airtel. The airtel number got activated on 4th january but there were no network signals for more than10-12 days. I went to the service centre on 17th january. People there swapped my sim but when the new sim got activated, i received a number other than my own number (Which belongs to someone whose phone was stolen & now he's disturbing me with his calls & threatening me). I went to the service centre several times but all in vain. They again swapped my sim but no use. I am not able to get my number back & this is creating a whole lot of mess for me. I want airtel to please look into this case & provide me a solution asap.