Over charging My cancelled fiber Account

I have been using Telkom fiber (Month to month) for the past 3 years till 31st of July 2025 because i was unfairly evicted from where I stay, I then called them first week of August and they kept on dropping the call then I sent an email of cancellation, but they have not cancelled it till now. they are telling me that I owe money for August and September from what they told me that you pay upfront for the fiber but now how are they charging me for an account that worked till 31st of July they are messing up my credit score as I now look like a bad payer with money that i don't even owe them