I have been having the same issue since coming to Verizon. After researching the issue I have determind that this problem is with firmware settings set by Verizon. All other providers when connected by WiFi calling will not autoswitch to cellular service resulting in dropped call when you leave the WiFi range. Verizon will switch to cellular when you leave the WiFi signal but will not reconnect when back when within WiFi range. Those of us that are in weak cellular areas will have frequent call drops because of this. If Verizon will program our phone to stay connected to the WiFi when the call is made or received this will no long be an issue.