You've provided zero info on your phone, and therefore made it impossible for us to really help.
1) List the first 5 lines on bootloader screen.
2) Is the phone modded? Rooted, bootloader unlocked, running a custom ROM (if so, which one)?
3) What carrier version?
4) How is cell reception in your area, typically?
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Phone: AT&T HTC One (M8)
Tablet: Samsung Galaxy Tab Pro 8.4 (WiFi only)