Charged $100 Residential Trouble Call, but I was never told this tech appointment cost $100, and the issue did not get fixed.

I was experiencing connection issues and unsure the cause after troubleshooting with an agent. We scheduled a tech appointment and I was never told that there would be any additional charge. I was charged $100 Residential Trouble Call and the worst part is the tech claimed the issue was fixed but I am still experiencing connection issues.  the issue the tech claimed was resolved, was not resolved. How can I have this charge refunded/cancelled?