Cybersmart NO response - I want to cancel!!!

Cybersmart recently claimed that my account is overdue. I queried that and they sent a "detailed statement" showing balance and payments made, dating back to January of this year. What it looks like is that payments are made every month around the same date. I sent through proof of payment for the last payment made and Kanyiso Tontsi responded that that payment was actually for October, not November and that I've been make payment very late every month and should relook at the statement he sent. I find it very strange because every single month for YEARS, Cybersmart sends an email for amount due in advance for the following month, which is payable within 7 days of receipt of the invoice. I make payment and then receive a thank you email from Cybersmart for the payment made. This has been the process for years - payment being made in advance for the next month. Never has there been an issue. NEVER has the account been in arrears. How is it that all of a sudden I'm behind a month? When I asked for clarity on this, they refused to reply. I've sent several emails after, and nothing from their side. I sent another email to find out how to cancel the account, received a response on what to do, did that, and then, once again, silence. What is their deal? I don't have time to be on hold trying to call them. And based on other reviews, it's hard getting through on call. Also, being an internet service provider, you'd think they have knowing how to email on their list of skills. Currently, they've switched the internet off, because if you don't pay by the 15th of the month, that happens. Strange how with all of my alleged late payments, the internet has never been switched off in the past. And honestly, if I'm in the wrong, I'll gladly pay what I owe. But at this point they haven't given me any proof. So annoyed!