John uses VOIP and has a cell phone antenna in his home to actually reach the tower. He gets dropped calls because of his location, even with a microcell. Leo says that one option is to look at AT&T or Sprint/T-Mobile to see if the coverage where John lives is better. They may have closer towers. He recommends talking to neighbors to see how their service is. Sadly, coverage maps are of little help like this.
Also try a different phone and see if the connection is the same. It could be an antenna issue in your phone.