Outbound calls being dropped every 15 minutes??

Other cellphone working fine, used an S4 did not drop calls.

No other devices in house.

there was a issue i was tracking there for a bit that only seemed to mess with Samsung phones..or at least semi newer ones and WFC..what i noticed at least with Sprint and Verizon Sammys was if the phone didnt have at least a small bit of a data connection through the mobile side WFC wouldnt work correctly..i didnt monitor it much through TMOs site but mainly through V and S.. it was something that Sammy changed up a bit with their phones after a certain update..no idea why seeing as how my LG G8 can have zero signal through the mobile side and as long as im connected to wifi i can use WFC just fine to take up the slack..

sounds like the issue you are running into however i cant prove its what you are seeing..main reason i think this is what you are running into is the fact that the room you have this issue in is the one where you get the worst mobile signal...if you go into any of the other rooms and you get a better signal then its working fine call wise correct with WFC?

again dont quote me on this one but again its something i have tracked for a while on both Sprint and Verizons sites...just not sure the same thing was happening on the GSM side