IM ONLY GETTING 20Mbps WHEN I AM PAYING FOR THE 1200Mbps

I am paying for the 1200mbps package and I am CONSTANTLY getting under 20 mbps. 1% OF MY DATA PLAN. 

This has been an ongoing issue since 11/2023 and xfinity has done nothing but replace the modem with an even worse one than before. How do I pay $100 for 1200 Mbps and only get 20Mbps,?? Thats absolutely revolting. 
All the resets, unplugging the router, and necessary tests have been done. I am at a loss of what to do here and am about to switch my internet provider because xfinity has always had some kind of issue with the way they do things

Does anyone else have this problem and can suggest something to do?