Night Mode Button Set Up

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I am new to the Siemens world due to employee leaving the company.

I am trying to set up night mode service button to allow receptionist to at the end of the day to play different message after hours. What steps would I have to take to set up new night mode service button on HiCom unit? There is currently a button set up already label RCOFF which I believe is used for DND, how would I set up a new button for night mode service like the DND?

Thanks

 

[Phoneguy7]

What model Hicom is it

 

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Siemens switch is an HiCom 300.