I am in Bangor Maine (04401) and for the last 2-3 weeks I have no data available. Even mostly-text services like google or email will not load, or load extremely slowly. I'm talking two minutes to load google search results for a restaraunt location. 
At first I thought it was a glitch, tried restarting or waiting, but it's been weeks with no improvement. If anything it's getting worse. 
The speedtest app says I'm getting 10MB down but after four minutes I still can't get a single email to load. Something's up. A hardware problem would affect a speedtest, right?
My phone is an iphone 6s plus. My plan is an old 40GB data plan that got grandfathered in at some point, since I've been a customer since like 2006.  

Any ideas for more testing I can do to try to narrow down the problem?