We live in a rural area with mediocre AT&T service and have been using a Wilson DB Pro 4g amplifier which has provided a fairly strong and stable signal for years. Suddenly, about a month ago, I was no longer able to make voice calls with the phone, but text and data are fine and the Mrs's 6 plus also works fine. When trying to make a call, my 5s shows a call attempt being made, but there is no ringing and after a few moments, shows call failed. Phone works fine once I get over the hill and into town. Updated to ios 11, restored network settings, restored factory defaults, replaced sim card - no difference. Thanks for any suggestions.