We've never had problems with AT&T mobile.
We used to have to go out on the back deck to make calls when we lived in an RF "hole". Keep in mind that low areas (in terms of HAAT, or height above average terrain) as well as areas that are surrounded by high, dense folliage--read that trees--are susceptible to bad connectivity.
While a transmitted RF signal at Low Frequency--LF, Medium Frequency--MW, High Frequency--HF, and VHF could care less about buildings and trees, UHF starts to get bad and all the cell phone bands 900 mHZ up to 10 GHZ are highly affected by it. Placement of the cell towers is also a factor. Keep in mind that your cell phone transmits a signal of 500 mW (typical), or basically 5 times the strength as your garage door opener (100 mW). That's not exactly big-time RF. While a ham radio operator can take that same 500 mW and communicate with the South Pole on Morse Code or digital computer modes at 14.030 mHZ HF (with a high gain antenna with height)...that same 500 mW at cell phone frequencies--also known as "microwave" frequencies doesn't have a lot of poop, and much less with heavy foliage and a low location--at least "low" in the eyes of the closest cell tower. There's only so much you can do with 500 mW and basically a glorified vertical dipole antenna...and it gets worse when people use a phone in anything other that a vertical position when on the cell tower's fringe.
I am lucky now. We moved to a nice mountainside home about 350' above the rest of the town around us and there are 2 cell towers--both we are far higher up than. We have 5 bars everywhere we go except 30 miles away in a major deadspot (no towers). Outside of that, we are rock solid everywhere we go. We go down to the shelter below the house (surrounded by concrete) and still be solid 5 bars.
