Pre Paid to Post Paid Connection

Location/place: Sinhagad Road, Pune

Name of company/service: TATA Docomo

Dear Sir/Mam
I got a call from tata docomo side that for convert my pre paid mobile no 8983744812 connection to post paid mobile connection, after many refuses i agree and given the my document & 300 Rs for post paid connection,executive visited my house and took all my signed document including 300 rs. tata docomo executive has said with 3 days your no will be convert into post paid connection, i asked for the receipt of 300 rs , but he did not given any receipt . When I complained to tata docomo customer care , executive said i have to visit tata docomo branch and solve the issue.
Verification has already done from tata docomo side.Now Please advise me or Take some necessary action against Tata Docomo .And ask them to return my money as well as all document.

Thanks & Regards
Shrikant Varma
#8983744812