Please stop debiting my account

I took out a month to month home router with mtn, It was advertised online as uncapped unlimited . Few weeks later the internet was out, called them to find out why they told me data is finished I told them how why because it’s unlimited they don’t me something I do not understand and they even wanted to debit the amount we didn’t agree on I was told is for the router but online they said router is free. But since I realised that I’m not happy with how they advertise their product cos it seems like they promise what they can’t deliver I told them I want to cancel . Another issue they told me I can’t cancel online I have to go to the store which was another red flag because I app**** for the router online why can’t I cancel the same way… since I couldn’t go to the store they continued trying to debit my account.. now I went to the store with their staff to cancel as they told me in store I was told I can cancel online however I told to cancel… but now they are still trying to debit my account I don’t understand why because I returned their router and I cancelled