2 modems in my account, cant remove/wrong icon in xfinity app

ooh where to begin, my main issue is ive been paying for 2000mbps speed for over a year now, i recently learned there is only 1 2gb port on the back of the modem for ethernet, after finding this out i had blazing fast 1800-2000mbps download speed, but seemingly out of nowhere in the last week, the speed has died to about 30mbps if that, terribly slow, prior to this, i had a technician come out, explained what happened, and more or less, when i now go into my xfinity app, and hit wifi, it shows a black box router, that is definitely not mine, and not the one i activated that i got from the xfinity store.

i spent 2 hours on the phone with xfinity a few weeks ago, and since then my account is "broken" according to the tech, he said he would suggest i cancel my account, and open a new one, because no one seems to know how to remove the dead modem from my account.

in this image, you can see for some odd reason, i have a voice modem with no serial number, and behind it is my current modem, my theory is the xfinity app is seeing this weird non-serial "modem", and displays the wrong info in the xfinity app, thus leading to problems even managing my network, and possibly my speed as a whole.

this is what the xfinity app shows, ive never seen this box in my life, and it isnt the one i have on my account, and i seemingly cannot remove it myself, and no one else seems to have an answer for me.

last month prior to this, i kept having issues activating and had to go up to the xfinity store multiple times, it was quite a headache.

to reitterate, my xfinity app is showing some weird black box instead of my modem, as a result i cannot actually view the info of the modem, and do other various things, options are missing here, and alongside that, i concur it could also be impacting my ethernet speed, as before this, the 2gb ethernet worked fine, but now the speed is pitiful.

Would appreciate any help at all, if i can remove the dead modem myself, or if support could, i hope it will fix the problem, thanks.