Fun tech fact:
Those “bars” don’t mean service speed. They represent how close you are to the tower distance wise. Quality of service, speed, network traffic, are all not accounted for.
Alright. My WiFi says it’s at 4 bars but it’s acting like it’s at 1 
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It’s actually a measure of signal strength to the tower, measured by the tower itself. The tower tells the phone how many bars to show based on how strong the connection to the phone is.
Yep, and metal etc. in a building or whatever can obstruct signals. I didn't know that the tower measured it though; that's pretty cool.