********** collection

I ordered a phone at Vodacom last year n then I cancelled my contract the consultant said she'll send couriers to come and collect it. The phone was collected then later I received statements then I called back n told them that I returned the phone, they said they didn't receive it it was ********** collection but they will conduct an investigation. Now instead of getting investigation reports I'm receiving letters that I must pay for the phone to avoid being blacklisted