I upgraded to XFI did the whole XFI and Pods for free deal was told my internet was fine when in my bedroom I get like 1 tiny bar and have to run a 100ft ethernet cord back there to get internet to the Xbox. Well lately my 300mps internet has speeds of like 44. Today tech shows up literally over two hours late again by testing with his app and phone says nothing is wrong and I must have old devices my xbox and phone are barely 6 months old, tells my son that if i'm not happy then I can request a new tech to come "fix" things. I pay way to much to have horrible internet and a rude tech. Also why couldn't I get the pods if my 3800 square ft house gets bad service? I guess cause after 7 years of only using comcast I should know that I will end up paying the extra 100 something.
so this could be a bunch of things. how old is the home? does it have any metal in the walls? if it does that will kill wifi dead. if it is a newer home that does not have this then you might just be far enough away from the gateway that you are getting a marginal signal.
if you are in the same room as your modem do you have a better signal and speed? i would take a laptop and plug it directly into the xfi this way you are by passing wifi and going hardwired. if it works hardwired than it is your home if you get poor speeds even connected then there is an issuw with your modem/router/wiring.
if you have "full speed" when hardwired that you need a better router. im not a big fan of plume as they arent really all that powerful and is only really designed to give way to the room you plug the pod into. check orbi which is the fastest if you want as much speed as you possibly can get or look into eero.
both of these options are very expensive because you are getting more then one unit. the main unit will plug into the xfi you then need to go in and put the xfi into bridge mode. once you have then that you can setup the orbi/eero. that should make your wifi better. if not then you live in a blackhole.
the secret of wifi speeds is that on a consumer plan you are lucky if you ever get close to the actual speed you are paying for. usually with overhead etc your download speed is cut in half,
if when hardwkred you don't get close to say 100-150 then there is definetly a problem with your line or unit. as a test have them swap out the modem for a new one.