Not very happy customer

Im disgusted with vodacom at the moment. My sister in law received a invoice of R500 extra this month for the number i am using ***. This was someone elses number and shows that i used 5gig in januarie and 5gig in februarie recurring on her account as it is under her name. Problem is i only use once off airtime?? I dont ever choose recurring. I dont have the app to buy airtime for this number aswell. My husband has a brand new number also vodacom yet strange people watsapp him which means it was someone elses number.But its a new number. I have proof that i never bought R500s data. Fix your problem.