Sony Ericsson — Service Center not giving mobile back

Address:

Mumbai City, Maharashtra

I purchased this mobile from Mobile Store, Powai on in March 2011, .
In one-two months started facing battery charging and discharge issues. Problem getting worst, I showed it to service center in Ghatkopar. Saying socket broken issue, they kept mobile phone for repair without warranty. Also they took some Rs300-400 from me. Now its been more than 3 years, I haven't got my mobile phone.

I have called service center hundred of times when I was in mumbai ( I am in pune for last 1 yr) . Always get same reply they will definitely call back with status but never call back.

Please help me with this. I cant even get my own mobile back in same condition.
Here are mobile and service center order details.

service center no :[protected]
Model Name - U20i IMEI - [protected]
Work order No - SW[protected]

Thanks Amit