No audio through earpiece/loudspeaker or microphone
Physical damage / water damage / outside warranty - arrange a repair.
If the handset is under warranty with no damage -
- Ask user to try someone elses' SIM in their handset (although it's unlikely to be a SIM issue).
- Ask the user to extract their data & perform a full reset - INSERT LINK HERE
- Arrange a warranty exchange LINK & ask them to extract their data.