Can You Sue A Company For Sending Bills After You've Canceled?

I wanted to try ADT home security back in February. So, I gave them a call and asked if I can cancel without obligation within a certain time period. The sales person told me I can cancel within 30 days. A few days later an ADT guy came to install it. He made me E-sign a contract. After reading it, it said the only way to be free of obligations I would have to cancel within 72 hours. So after about 24 hours I call ADT to cancel it because it's not very useful for my situation. The person tells me that they put in the request and that it's within the 72 hour period. They also say someone from cancelation department will be calling me back in a few days to set up the appointment to uninstall the equipment. A week later, and no one has called so I call them back and they tell me that I never called to cancel. I told them the exact date and time. They begrudgingly agree that I called within the 72 hours and set up an appointment to pick up the equipment. They come pick up the stuff and all is good. Few days pass and I get a bill for about $780. I reread the contract and it clearly says that there's no obligation from me if I cancel within 72 hours, and it says that if ADT doesn't make a good enough effort to pick up the equipment that I can just toss it.

So I keep calling and they tell me the cancelation is still processing, ignore the bill. Month later another bill for same amount. I call back and they say that the bill is for the equipment that they picked up. They say that even though they picked it up that I agreed to pay for it. I tell them I want to talk to legal department. They say call back in Monday. I call back on Monday and ask to speak to supervisor, they refuse and tell me theyll make sure this all gets fixed. They say it's been processed and all is good.

Today I get another bill in the mail again. Same $780. They'll probably send it to collections at some point. My question is if I have grounds to sue this company. I always end up spending a couple hours on hold while they "look into this" and "fix it." They're probably gonna blow my credit score, and I'm thinking about buying a house soon. The time and money I'd have to put in to get a lawyer and pay them to fix this would probably be excessive for what this is. I'm somewhat versed in law, I guess. Is it possible to file the case myself? As far as I can tell there's no gray area. Seems pretty clear cut. I'm pretty sure they record all their calls and I could request those recordings in discovery.

Any advice is appreciated.