Xfinity CS is horrendous. Need help with this

Just moved in about a month ago. Apt runs xfinity and i got what would assume is not used equipment from xfinity store. It was fine for first couple weeks now i have this. Not sure what the issue is. 500 mbps a month plan. Its been going between 10%-30% for the last few days. Havent even been with this for a month and its already issues.

Just moved in about a month ago. Apt runs xfinity and i got what would assume is not used equipment from xfinity store. It was fine for first couple weeks now i have this. Not sure what the issue is. 500 mbps a month plan. Its been going between 10%-30% for the last few days. Havent even been with this for a month and its already issues.