xfinity can't hold a stable connection for more than 5 mins and there support cant help.

xfinity 100 is what im paying for

it connects the deconnects. anytime i try to use the internet, my download speeds stay high but uploads go up and down making it look as if it has any uploaad speed when it doesn't. 

I had to connect to another internet provider just to even get on to this support forum.

i have been told to replace the modem which xfinity provides and i have gotten xfinity to replace it several times. there has been no help otherwise as when i call i get put on hold til the system auto hangs up on me. 

so i need help. fix my goddamn internet please, somehow the hotspot of the modem is faster and more stable than an ethernet connection to it. and i have used several different ethernet cords each and as i mentioned earlier different modem/ routers.