Complaint

I had a month to month data contract with cellc then i was not aware that when i reach last month of contract it will keep on going, then the money started changing from R250 to around R850, i called to enquire and i was not assisted. I then skipped a month not paying and they closed a simcard while still billing me and i wasn't using their data at the time because the simcard was deactivated. My question was "how do they still bill me while im not using their simcard as the deactivated it" i called them spoke to their team leader and later manager. I was told to cancel my contract i did cancel which they told me it will take 30days, and apparently they canceled the cancelation, under who's concern i don't know, now they say im owing them R4000 i ask them to send me records of when last did i use their data and how the money got there and im not assisted I'm told that of i don't pay ill be blacklisted.