This S6 on Sprint has been quite a challenge and has never felt like a flagship experience. Basic network connectivity, wifi/network handoffs, default voicemail app, and caller ID all had or still having problems. I recently spent 1 and 1/2 hours with tech support on the phone, through 3 levels of support in India, then transferred to the 4th level back in the US, and no resolutions. A promise to call back 2 days later that never came. Forget everything that phones have become in terms of mobile computing, if the basic phone functionality of receiving calls, caller ID, and voicemail don't work and cant be fixed through 4 levels of tech support; you need to refocus and reprioritize what you see as acceptable.
The latest is I update to nougat and now wifi calling never works. My phone is literally sitting 2 ft from my wireless router, and it says wifi calling is unavailable even though wifi is currently connected to my home network. Same thing happened at work. I didn't have this problem before. Wifi calling was one of the few things that worked, and critical to managing shared minutes amongst 6 phones.
First I have 3 S6's and have never had any major issues so Everyone experinces will Alawys be diffrent no matter what the device may be. Which sometime this week I will be moving over to the new S8.. First not everyone will have their phone settings set the same, Second not everyone home network area will be the same some will be better than others. Thrid not everyone will have the same kind of Apps installed which some Apps can cause people phones to act a little diffrent as well. I never use Wifi Calling due to my home area network is always good that I had no need to use it. With the kind of Plans Sprint is offering folks should be able to be on plans where they should Not have to worry about sharing data or minutes which emilinate having to worry about those things. So saying all of that what kind of error messages are you getting when you try to use Wifi Calling??