Try to disable always on display feature and close all background apps. and do not use apps like Clean Master or CM security or Du battery saver, Facebook and whatsapp because these app drain your battery very fast and after closing them they are still in process in background.
---------- Post added at 11:19 AM ---------- Previous post was at 11:15 AM ----------
The best launcher fo S8 is Only Touchwiz Home and Other Launcher are not recommended
That works on some S8, but on mine and others like mine, that option doesn't show up. That's why I gave the tip aboveSeems to me like we can also change this setting without nova (off-topic: although I use it as well, great launcher, especially the latest beta), go to settings - connections - mobile networks - uncheck VoLTE calls.
Best Regards to all