Airtel — someone hack my no

Hello i am harsha tahiliani... I lived in jaipur raj.. Where i purchased airtel 4g sim about one year ago but now i am living out of country so my no has changed... Ths sim is not using... But this no91 [protected] i was using it only for whtsup... Today i updated my no with belize country but someone is misusing my old no and sending weirded message to my contacts and mi’s use my identity... It’s a humble request plz trace him or her and block the all no of ths sim registration... Thnx and help me