Recover deleted message gigaset dx800 - Siemens Gigaset 2420 Phone

Question edited for clarity.
Question moved to Gigaset C300.

You need to do a power reset. Do the following in this order.

Remove the phone plug from the wall jack.
Remove the handset and remove the batteries.
Unplug the power adapter from the mains plug.
Put the batteries back in the handset observing polarity.
Plug the telephone line jack back in.
Plug the wall adapter back in.

It should now be reset.

Page 34 refers to deleting SMS Messages. You know these are TEXT Messages and NOT Answer Machine Messages?

http://gse.gigaset.com/fileadmin/legacy-assets/A31008-M2203-Y701-2-7619_en_SGP.pdf

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Question edited for clarity.

Gigaset A58H phone handset display reads "SMS mem. full Del.

https://www.justanswer.com > ... > Phone Problems
Apr 1, 2020 - You can ignore any phone call offers that may pop up - they are sent automatically. . To delete the SMS messages, open the Message inbox, then ...

https://www.google.com/search?q=Gigaset+A58H+how+do+I+delete+the+message+%27SMS+mem.+full%27

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Press 0 during message playback. See "Deleting an individual message" on page 8 of the manual: http://www.gigaset.com/fileadmin/legacy-assets/A31008-M2401-L101-1-7619_en_UK_IE.pdf

It is very easy to lost or delete important text messages from Samsung Galaxy S4 by accident deletion, carelessly resetting, rooting and other reasons. Actually, these deleted messages can be restored from your Samsung GALAXY S4 (GT-I9500/GT-I9505) at ease.

My dear:
Very Best Solution:You Go To Service & Sim Office and Get The Puk code And Pin code From Office oprator
Enter The Puk code and Yes
Enter The pin code and Yes
So Puk code Open and Problem will Quickly Solved
But:
Don't try to enter a PUK code without knowing the right one.
You need to call your service provider to get this code.
It can be as many as 8 digits, and it is random. If you enter too many wrong codes,
you can permanently damage the device. So Please You Go to Service office
and Get the Duplicate Sim From Office Oprater Same Your No Problem will Solved

You can open messages and choose the option to MARK all the messages on the BOX -ONLY if you want to delete them all.
Once marked choose the option to delete them fully.

Hi did you get this fixed? I am having the same problem.

http://download.gigaset.com/repository/1275/127598/A31008-M1801-A601-1-UZ19_17-11-2008_en_ARE.pdf

Above is your manual .If you go to page 11 this is the start of deleting messages.

Hope it helps!

On the fax press function and the number 7.
Then there is a seperate monitor button that needs to be pressed 4 times.
Next press * and you will see in the display that you have entered into service mode.
press the down arrow until you get to #6 ram initialize and press SET.
arrow down until you see ALL JOB CLEAR and press * this will show ram initialize for a few seconds and then go away. Memory has now been cleared.