Slow and disconnecting all the time

I’ve tried to post here 20 times and it keeps saying please retry and deletes everything. I have gigspeed internet and I’m getting 150-250mbps. My phone won’t even load pages unless I turn off my wifi and use data. All of the Xfinity apps are telling me that everything is fine, but all of the 3rd party apps are telling me I’m getting slow speeds. I keep getting disconnected and or the loading wheel while trying to stream. I’m paying way too much money for this service to have instability and I’m getting frustrated with the AI runaround and lack of real support staff. I’ve tried all of the troubleshooting steps, none of my devices are more than 40 feet away. Everything was working great… for a month… and nothing in my home has changed. Why is my speed being throttled?? I have unlimited everything.