Billing issue

Worse experience I’ve ever dealt with from any company. I haven’t had service since two years ago. I paid off an over due balance by logging in and making a payment just for yall to say it was the wrong department and now I have to wait for my money back for yall to send it to where it’s supposed to go. Now collections are requesting I pay them the same amount I just paid yall. And I paid them another due amount that yall sent my device to them even after me trying to return the phone to you all way back when I canceled the service for the phone and internet. Y’all took the internet equipment but not the phone. So then I was left with a device I couldn’t use and still can’t use after even paying for it because of a locked SIM card. If I need to seek legal action I certainly will because I refuse to pay another penny and can’t get a clear answer to random charges that are being put on a service I didn't agree to have that was setup without my agreement.