Insane Wi-Fi Billing Issue

This is wild. I moved to a different state, their WIFI didn't cover the area I moved to, so I had to cancel. Called, said I wanted to cancel my wifi, they told me to do so. Ok cool. This was in July. It is now October, and they are still charging me for WIFI. Called again last week, ok, they said it was a mistake on their end and sent a credit request of 100, that's great. The issue comes when my bill is $200, when I only have one line, which is $60, and an Apple Watch cellular plan, so my bill should be between $60 and $90 with tax. But my bill is $200. This is more than double what I actually have, and  I just called support today, and they're absolutely useless with an attitude. I am being overcharged because of their mistake, and the person on the phone is making it sound like I am the problem. No, you drone, your company messed up. I've been here almost 4 years, and it's wild, such a simple issue can't get solved. I canceled my wifi, so my bill should reflect that. It doesn't. Now they're threatening to turn off my service because of an unpaid bill. Why would I pay the entire bill if I canceled the service? You're charging me for something I no longer have, and then threatening to turn off my service because of your mistake, which you admitted to. What is the point of mailing a check and not just applying it to my balance? So I have to wait, god knows how long, for a check, but I have to pay out of pocket for their mistake as I wait for this check? What? This is so silly, and I can't believe this is such an issue. This really makes me think I should switch services; this is ridiculous.