AT&T and Verizon are the worst where I live. I can't get any data whatsoever to come through and if I manage to get any at all, usually in the middle of the night, I get edge speeds. Occasionally LTE will light up but I get nothing to come through.
I gave up after six years, broke my last contract and moved to T-Mobile. I use them on my 5S and Mini. I get speeds I only wished I could get on the other two carriers with T-Mobile.
This screen cap and test was taken less than a mile from my house. Bad AT&T, just plain bad.