Wrong amount billed, account not cancelled

I cancelled my ADSL contract in May, on 15 June 2017 when I moved over to LTE, I was told it was cancelled and I was credited R690.00 that was billed, end of June I was also billed, R201.01 was credited to my account, in August R503.51 was billed for the same account I cancelled in May, when I call the call centre I am told it's been cancelled but when I spoke to the billing department I was told the internet was not cancelled, I am so tired of calling them, I even want to cancel the LTE account as I am fed up with their pathetic service.