Unable to turn of screen while making WhatsApp or skype call on loudspeaker ios 10 update
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This doesn't happen to me on my phone, so it must be a bug or something ...
I wonder if this is similar to this issue: Unable to turn of screen while making WhatsApp call on loudspeaker io10 update
have you tried closing the apps and restarting the phone?  You can quit the apps by double-tapping the home button, swiping the app UP (I would do this with WhatsApp and Skype), and then holding the power button until the option to turn the phone off comes up - swiping on that, and then starting the phone back up?
try a forced restart of the phone.  Hold the home and power buttons until the phone just seems to shut off; continue holding until the Apple comes up.
I would backup the phone, wipe it, and restore from the backup.