Vodacom Phone contract

I am writing this email in regard to the amount that Vodacom claims that I am owing. I signed the 24-month contract for a cell phone with Vodacom, of which I believe in that 24 months the cell phone was paid in full; the only additional benefit was R125 airtime, of which the SIM card was also disconnected/blocked late September 2022. Since then, I have never used any services of that SIM card. It turned out that Vodacom was still billing the account while the sim card was disconnected and the cellphone was fully paid; after 3 months, Vodacom indicated to me that i was owing them R3300. Please assist.