Unprofessional and ********* billing department - Beware, check your statements!

Unprofessional and ********* billing department. I cancelled my contract more than a year ago (November 2022) when I moved to fibre with WebAfrica. Confirmed with a phone call with the after hours desk. Worth noting I paid by credit card every month while making use of your service. Today I receive an sms stating I need to pay my account before 20/11/2023, no amount specified, or I will be handed over for debt collection. That is in less than four days. I log onto your website (my credentials still work?) and see a failed debit order. Huh? I paid by credit card?? I have exhausted all contact options available on your site, ticketing system, email, phone calls and WhatsApp numbers (yes there are more than one) and even Facebook, trying to get clarity, or just a human response. No reply except "You have entered an invalid response". This is unacceptable, not even sure it is legal. Not one attempt at contact me on my phone, whether phone, WhatsApp or sms. Not one email. Please explain, I will not let this just carry on and will challenge it. You cannot just hand over someone like that. Do you even still exist???