To setup a central voice message, you can do following:

Record a short message in wav format:

• Format: WAV
• Channel: Mono
• Bit rate: 8 kHz
• Sampling: 16 bit

https://www.3cx.com/docs/converting-wav-file/

 

Create a digital receptionist

Click Digital Receptionists, click Add button.

Give it a name, click +Add and find the wav file you created.

Under Menu options, leave nothing for all keys.

If no input within seconds: type 1.

Action select End Call.

Click OK to save.

 

Basically we don’t want anyone to have time to select, just want to leave a out of office message.

 

Edit inbound rule

Go to inbound rules, click the existing rule for your number.

Destination for calls outside office hours: select the ext number you created for the digital receptionist above.

Set up Specific Office Hours for this rule: setup your schedule.