Please perform the following steps to resolve the issue:
1- Make sure that 20% internal storage is free for which clear the RAM memory and storage of device (Settings > Device care > Memory/Storage > Clean Now).
2- Settings > apps > phone app > storage > clear cache.
3- Perform Interactive checks through Samsung Members Application (Samsung Member> Get Help> Interactive checks > mic).
4- Stop the background running app (Tap on the left soft key and close all the running apps).
For further assistance, register your concern in Samsung Members Application (Open Samsung Members Application > click on “+“icon > send feedback > error report/ask questions).
Team Samsung Members