Next time your internet connection feels slow, do this test:
1) Connect your phone directly to the router via WiFi, standing right beside it.
2) Run a speed test (Fast.com, Speedtest by Ookla).
3) If the network speed is good there but bad everywhere else in the house/office. It's likely your WiFi coverage, not your internet plan.
4) If it's bad even standing next to the router, then it's time to have a word with your ISP. Call them right away.

Knowing which one it is means you skip the back-and-forth with your ISP entirely. You go straight to the right fix instead of losing a day waiting on ISP support for a problem that's actually sitting in your living room, or moving furniture around when the real issue is on the network side.