I have done this. I have been to Sprint store twice. Called Sprint support. Called Samsung. I think there is an issue with my phone but not identifiable when at the store. I know S5 has Bluetooth issues but I have done all the steps Sprint, Samsung, or blogs have said. Sometimes its fine other times not.
I apologize for the delayed reply. Have you tried using a bluetooth device from another manufacturer to see if it has the same problems? How long have you had your Galaxy S5?
Sprint Social Care