Siemens HiPath 500 Operating Instructions Manual page 26

Text Messages (optiPoint 600 office Only)
Step by Step
US:F3=Clear
UK:F3=Delete
US:Save
UK:Confirm
26
or To delete the message:
Select and confirm.
Confirm your entry.
On the optiPoint 500 entry, optiset E entry and
optiset E basic models, text messages that have
been sent are signaled as a callback request; the
Message Waiting LED flashes.