Billed for services I didn't want!

In January I had my service reconnected. I decided to go into the local store to do this to be sure I was getting exactly what I needed for internet services. I explained to the Comcast employee that I wanted the UNLIMITED INTERNET ACCESS and to be able to stream internet to my TV. I told him I was willing to pay the extra $30/month to avoid overage fees because in the past the overage fees started to get out of control and I did not want that to happen again. He asked me if my kids were gamers and when I responded "very much so" he told me I needed to be on the UNLIMITED plan, and it would not be a problem. He said my bill would average about $140/month which includes the $30/month UNLIMITED plan charge. Fantastic I thought! I did get a few notifications of going over the limit, but I just figured it was part of the billing system and it would reflect on our statement. The bill was paid on March 15, 2021 in the amount of $255.34 and as of today there is a balance of over $400 which includes overage fees for $100. I decided to look back on the paperwork from January when I signed up and it is completely wrong! I was very blunt and insistent when I signed up for service that I wanted the UNLIMITED PLAN AND STREAMING TO MY TV ONLY, no more, no less. I also made it clear I did not want to be entered into any contracts. The Comcast employee assured me that he understood and everything was as I wanted, only its not! I went back to the local Comcast/Xfinity store to get this straightened out but was told I had to call. It is impossible to get through to speak to a human that understands and speaks english! I've tried finding an email address to write to, but no luck there either! This is very frustrating and wrong. I have kids who are virtual students so I can't lose my internet connection, but I also don't want to be liable for services I did not request and can't afford.