DATA BUNDLES CHARGED ON INACTIVE NUMBER

I just realized that I am paying for a data bundle every month for the past 6 years for a number my son used 6 years ago. I never activated this data bundle and cancelled this number 6 years ago when my son moved to Australia. This number is not even activated on Vodacom system, I was told they cannot cancel it bcs the contract does not have an end date. I managed to cancelled this contract again today, after they fixed the date thing, but I want a refund for the data bundles I was charged for for 6 years for a number that did not exist on Vodacom system.