AT&T Fiber Barely Works- Spent 10+ hrs with Customer Service Just Being Passed Around to No Solution

My husband and I recently moved to an area in a major city with AT&T Fiber.  We decided to go with it and immediately had issues with it.  We don't live in a big house, ~1800 sq feet, and our initial recommendation was to get the WiFi extender.  We did, nothing changed.  We've even had someone come out and they basically left saying there is no way to tell if the extender is working or not.  So, $50 down the drain.  We've spent hours on the phone with customer service and tech support, only to waste our time and keep repeating the same "this is what's wrong" story top no solution.  We have trouble streaming anything, the WiFi on our phone barely works so most of the time I just turn on cellular data when i'm home.  At one point we talked to someone who said there is no reason you should need an extender in that size house, fiber should reach out to around 10000 square feet and be fine and speedy.  So long story short, how do we escalate this issue to actually get something done and get what we are paying for?  Any help appreciated.