Please tell us some basic information before asking for help:
Thank you for your asking. Kindly provide the information below so that we can better assist you.
1. Is your current firmware version WW-188.8.131.52?
Settings>System>About Phone>Software information
2. Does the situation happen in Call app, Whatsapp call, Youtube, or all kind of speaker related apps?
3. Please try to enter "Safe Mode". If the function works well in Safe Mode yet the issue remains out of Safe Mode, please check on any disturbance from the installed 3rd party apps.
# How to enter and exit "Safe Mode"
4. Does the situation remain the same after performing "the Factory Reset" ?
Settings>System>Reset options>Erase all data(factory reset)
Please note that once the Factory Reset is completed, all data, apps, settings and personal information will be deleted.