AASTRA DT4x2 for MX-ONE User Guide EN - Manual (Page 78)

Messages
DT412/DT422/DT432 78
To delete a message:
Delete
Press (see display).
Delete message? is shown in the display.
Yes
Press to delete the message (see display).
If you get a text message with a request for answer, the text
Acknowledge is added to the message. Use the Soft keys to do a
positive or negative acknowledgement.
Note: The option Delete is not available for a message with
request for answer. An unacknowledged message can only
be deleted from the message list.
To reply to an incoming text message:
Reply
Press (see display). å
Send
Enter the message text and press (see display).
Sending is displayed as a confirmation of the transfer.