I’m being billed after service is fully cancelled

I was billed after I cancelled my service. I had paid for the entire month and cancelled before the next bill was sent out. My equipment was returned the very next day so again before the next billing date. I cannot get a single person on the phone as that I no longer have an account. The automated system is terrible and feels like a deliberate way to make it impossible to talk to an agent with any sort of question. It feels like Xfinity is deliberately still taking money and making it hard to get it back when they are not owed it.