Mtn stop taking my money

My contract ended in January 2026 and i canceled it and returned the router. To my surprise mtn continued debiting the money, i phoned customer service and the agent logged a complain and told me i will get a call back from mtn. I waited for the call till i decided to call back mtn and they told me i owe them R5000 for not returning the router and if i did i was supposed to send them IRMS number. I went to the outlet i took the router to and the guy that assisted me checked on the system and he showed me that it is back at the warehouse. Mtn i want my money and stop taking my money i don't owe you anything!!!