Net pack got activated on my vodafone post paid number without any prior intimation via mail or message

Vodafone company activated net pack (data pack) on my post paid number 9051777783 without sending me any mail or message. When I mailed them for clarification they said that there has been no discripency in the bill and closed the case from their end which is beyond my understanding. They are not ready to credit the extra money (INR 1897.74) that I have already paid for the service that I have not at all used.