So sorry for this annoying trouble caused by the latest system update.
We’re actively working on the fix, please follow the following instructions to get the work around first:
1. When you accept an incoming call, press “Hold” button once (on upper right of those 9 buttons)
2. Then immediately press it again, and then you can successfully talk on your phone
This issue only happens on the incoming call(MT), it works good for the outgoing call(MO).
Sorry for the inconvenience, we’ll fix it soon.