Complaint - unhappy customer

I had a cellphone contact with them which was for 24 months, I paid it all off and it ended last month which was in August. I then went to two branches to have my account closed and I was told that I need to call the contact center because they don’t do cancellations. I tried to contact the contact center however I didn’t receive any assistance, I went to one of the branches again today and they called the call center on my behalf. The agent that we spoke to was so rude and unhelpful, she told me that they are going to debit my account again I asked her for what and she couldn’t answer me instead she kept on being rude. I am beyond livid and I want this to be escalated I can’t keep on paying for something that I’m not even using. I asked to speak to her manager and have this escalated and she didn’t want to escalate this for me. She told me if I want the contract closed I must pay