Bad service and charges when cancelling the line.

I have been a client with Clear Access over 5 years. I cancelled my fibre line in February and gave the a calendar months notice. I signed a contract with them in 2019 and in 2022 I moved and requested my contract to be moved. I was told that I could not transfer the contract and that I would have to sign a new contract. I adhered to the procedures and I accepted the terms and conditions via email in 2022. I also confirmed my package via email. I was not asked to sign a new contract. Now when I cancelled my line, they asked me to return the router in its original packaging which I also adhered to. They credited the router and then invoiced my account for the router. They said the new terms and conditions stated that the router belongs to them and it is their property so I should return it. I do not have a signed contract with them and now they have updated their terms and conditions. I accepted the terms and conditions in 2022 and they changed their terms and conditions in July 2023. I have sent numerous emails and phone calls requesting management to look into the matter but my emails are not escalated. I have followed all their procedures and even comp**** by sending back the router, which was not in the terms and conditions that I accepted. And now they are charging me for a full month and will not take any responsibility for the admin that was not done on their side.