I’ve haven’t seen or experienced this myself, so if you got it: please use my Let me know form so I can know a little more about it.
This have been said by HTC today (Dec 17th 2014) on a reply to a question. This and similar replies.
We are aware that some HTC One (M7) users have recently been experiencing audio issues making network calls on their devices. Neither WiFi calling nor other HTC devices are impacted at this time. We’re working around the clock with our technical teams and partners to resolve the issue as a number one priority. We will provide further updates as soon as we can. For anyone experiencing this issue with your HTC One (M7), you may want to try WiFi calling, and we ask that you please contact your local Customer Care
It’s our top priority right now and we’re working to fix it. In the meantime, please use Wi-Fi calling or pop over to our Customer Support team for some advice: http://bit.ly/PRew6n
I’ve looked around but I can’t find a One M7 that got this issue. So, if you do got this. Please comment below, and please include just what kind of device it is. Like regular/network/carrier/etc. Include CID if you do know that information.