Clueless and Useless staff

I cancelled my fixed line ADSL subscription 2 March 2020 using the provided Cancellation functionality on the company's useless WEB portal. Received confirmation SMS and email messages. I was prompted that I would need to pay the last month after cancellation, which I did 30 April 2020. This account was therefore cancelled and all outstanding amounts settled.

Suddenly I have debt collectors harassing me for unpaid amounts on the account, due to the ***********s staff employed at this institution. WHATEVER YOU DO - DO NOT ENROLL FOR ANY PRODUCTS AT THIS USELESS COMPANY!!!!