debit on my acc without my concent

I had a contact with them,, 1st month was great,, then no signal anymore,, tried so many things,, after about 5 months i said no,, this is not gonne change,, and i candled my contract,, had to pay a extra month cause i was to late for the cancellation date,, so i did, now,, about a year later they debit my acc R2499,,5 times my monthly premium, asked them why,, they said i did not pay 3 months ,, never did i receive any amount outstanding,, I want to know if im paid up in full..