Billed and Charged (autopay) after FIOS Cancellation

I called to cancel FIOS service, effective August 31, 2023. 

I was just billed today and charged (autopay) for September service. I've been told the billing policy and the statement date was August 28th. 

I would have canceled before August 28th, had I known that I would be billed for September. I just chose the end of the month, thinking it would be the most effective and efficient way to end service. 

However, I spoke to the agent today who told me,  about the billing/statement policy and that there was nothing I could do. I turned off autopay, just in case they tried to bill me again in October. 

I was never informed of the policy. Like I said, I would have canceled service sooner, had I known. I didn't need it past the 25th anyway. 

Any way to get this resolved, considering I wasn't informed?