To get things moving, you should probably log in to your router first,
http://192.168.1.1/, find those line parameters, and then just drop a screenshot right here so we can all take a look and chat about it.
Honestly, you’re likely going to need a technician to come out and physically inspect everything—checking all the connections, the terminal points, and your specific DSL port at the local exchange. If the stats look perfectly fine on paper but suddenly tank once the evening rush hits, then we've found our culprit. It usually boils down to issues within the underground cabling; since AT&T transitioned everyone over to VDSL, we're dealing with a much higher frequency spectrum that was previously untouched, and now everyone starts interfering with each other's signals the moment people turn on their TVs or start heavy downloading in the evenings...
There isn't really a "fix" for that kind of thing, unfortunately, because you're going to run into this issue regardless of which provider you use. If they can't actually resolve the underlying connection problem, the technician might be able to get you approved for a Spectrum mini setup or some mobile data as a workaround.