Change name display on Toshiba DKT2020-SD

I am assuming you want to change the display to read another persons name, or blank. If that is correct:
Press a [DN](labeled intercom on my system) + #621.
That opens edit mode.
an example. My phone reads "MARK 29"
where Mark is the user, 29 the extension. John replaced
Mark, so target is "JOHN 29"
so intercom # 6 2 1 puts me in edit mode
# toggles between alpha/numeric
* moves the cursor, I repeat * until cursor is under M
Hit the 5 key, changes the M to J and moves cursor under the A.
Hit the 6 key, the A changes to M, and the cursor moves to under the R. I hit 0 which changes the M to N. I hit 0 again, the N changes to O.
Hit the 4 key, the R changes to G. Hit 0, G changes to H.
Hit the 6 key, K changes to M. Hit 0, that changes the K to M. Hit 0, M changes to N.
We are done, as the extension number stays the same. Hit spkr key to leave edit mode.
Hope that helps!
# toggles alpha/numeric

I know this thread is old but I was currently trying to figure this out myself.

Before we had a new phone system installed, I could change the name on the display by hitting #621.

With the new phone system, #621 disables call forwarding and displays the message "Data Programmed."

Now, I have to connect to the phone system with a program called Strata eManager (which includes a web interface) and edit the station:

Login to eManager
Connect To Client Equipment
Click on Station > Station Assignments
Click on the extension that you want to edit
Edit the "Name To Display"
Submit

Here is a link to download the eManager software:
http://www.connect-comm.com/NetworkeManagerV5.20A11a.exe