Worse ISP Ever!

I had a month to month contract which I got online, they delivered the device to me but when I cancelled online they told me I should go to the store to drop the router which I did beginning of May, it still hasn't been cancelled, when I called yesterday they told me I need to call another company that opened this account, someone explain why is MTN is still billing my account where as I disconnected it over a month ago REF IRM***5

Also my LTE line I get billed twice, R750 and R96 when I called they told me they don't know, they will refer, I need someone to do their please REF ***