I'm confused by cell service

[BOP]

So I'm looking at this map: http://www.deadcellzones.com/att.html#.VzzP076vZaU and it looks like Lusby is covered by Verizon. You'd think that I'd have great signals, but you'd be wrong about that. It's baffling to me as to why, with what looks to be 5 Verizon towers in the vicinity, I have to keep a land line so I can make and receive clear calls about 99 percent of the time.

 

[TWL]

Those 5 red dots aren't cell towers. If you click on them, you will see that 4 of them have customer feedback complaining about no signal. The 5th has no comment but I assume it was meant also to complain about no signal.