Unhappy about Cell C service provider account

After 2 phone calls of 12 minutes and again 42 minutes on a call to cell c, I was shocked to hear that my wifi was suspended because of accumulated fees from Oct 2019 until now of which I was never informed. I phoned on a couple occasions in wich I confirmed with Cell C that my bank details have changed and that I am now paying via eft. They still debited my old bank account and now I need to pay for bank fees from Oct 2019. Why did they never sms or email me in connection with the debit orders that was unpaid??

Now, in this time Im without my wifi service and need to pay a huge amount before they will reconnect. It is truly unacceptable. I want proof of their so called messages and emails that they allegedly sent.