My bill is wrong.

This is my fourth time reaching out now about my bill being almost $200 more than its supposed to be. I changed my plan almost 2 months ago to just internet. I'm still being charged for television and all the boxes which I returned to the store the day I changed my plan. I don't even have the modem I bought my own. I was supposed to be refunded the difference instead I received a credit which is still almost $100 less than its supposed to be. My current upcoming bill still shows the wrong amount and charged for services I do not have. I've gone to the store and talked to representatives online. Who can I talk to since no one has helped me at all? I want my money back and to stop being charged for services I do not have.