iPhone 6: No sound on headset for random calls

[cam254]

When I make a call on my iPhone 6 iOS 8.4, about 20% of the time the call connects but I cannot hear anything. The person I've called can hear fine, but I can't hear, as if the speaker is dead. Only advice I've received that works is clicking airplane mode on and off then trying the call again. That works well. But a few calls later it's back to the same thing. Especially likely to happen if I click from within a contact, link, etc rather than typing in a number. Any ideas? Thanks

 

[C DM]

So is this only when using a headset (vs. using the regular earpiece next to the ear or speakerphone)?