Extremely unprofessional employees from billing department who must be trained about customer service

I had a month-to-month contract with Telkom for approximately 3 years where i paid at the beginning of the month On the 31st of July and beginning of August I have been trying to reach them telephonically, but the consultants kept on dropping my call when it's my turn to call and wasted my airtime. I wanted to cancel the month-to-month contract and the fiber was switched off by the 31st of July 2025. But now i am receriving statmeent stating that I owe 2 month instalment for a fiber that was not used for the past 2 months i kept on asking if how do I owe the amount and they are failing to explain or call me and hence that their customer service employees are cutting the call I am not prepare to keep on calling them. Now they are messing up with my score as this will keep on appearing as a non-payment. Now they are failing to explain to me via email and are demanding for me to call them which is extremely not professional