Cancel **** no plz

I had a old contract no which has been converted to a top up no which i subsequently stopped using. This no *** has been allocated to someone else according to the staff in vodacom shop. last night all my contacts received a whatsapp mess from this no asking for money , pretending to be me. i asked staff at vodacom shop to cancel this no completely , but they responded that i must complain on hellopeter to get vodacom to cancel this no. Sovodacom plz cancel no *** as **** operation are being conducted from it.

Thanks