I am having the exact same issues with my extender which is also a Samsung 3G model. We have had the same extender in the same location with no problems for several years. Just recently both my wife and I have had the same issues with both outgoing and incoming calls. You attempt to call out and it takes sometimes multiple attempts to complete a call, sometimes it just hangs up without connecting, sometimes it shows that it is connecting but never rings and no one on the other end but they will tell you they received the call and were speaking. On the incoming calls you can answer but no one is there, this may happen 3 or 4 times in a row with the same person and they hear you! This has become extremely frustrating for us because we both work from home. We both have iPhones 6+ and 7+ and have done the #48, restarted the Network Extender, powered the phones on and off, to no avail. We have no signal where we live without the Extender so signal issues cannot be the caused. I am not sure but I believe it may have began around the time of the iOS upgrade to 11 although I cannot state that for a fact. Any help would be really appreciated!