My wife has a S21+ and she's using the Samsung ear buds I received as a free gift for my S22 Ultra.
Her friends complained that their calls were not going through to her, also, the WhatsApp voice messages she received could not be heard on her phone.
The source of the problem - she removed the ear buds from her ears but didn't place them in the Samsung holder / charging case, she placed them loose in her purse.
Calls would come in but would go to the ear buds. Once we placed those ear buds in the charging case, she could hear all those 'blank' recordings in WhatsApp.
I only stumbled on this solution as my wife had a notification on her phone that her ear buds were at 13 percent and needed to be charged. That got me thinking about the ear buds.
That put me on the track of either turning off Bluetooth or placing the ear buds in the holder / charging case.
Problem solved. 
