Dramatic speed drop

Recently, work was done on the tower close to where I work. I use my phone’s wi-fi hotspot to link my personal computer for internet use. Has always worked very well with average download speed here are work of over 25Mb/sec. (At home, different tower it’s over 160Mb/sec as the tower is closer.) Nonetheless, speed at work has now dropped to substantially less than 5Mb/sec no matter where in the building I’m located. Can’t seem to communicate this to the Customer Service rep who doesn’t seem to have any grasp on what I am talking about.

Any suggestions?