Handle calls outside working hours, collect voicemail, and forward calls.
Go to PBX → Business Hours and add a schedule with your working days and times. Use it to send callers somewhere different when you're closed — for example to voicemail or an out-of-hours message.

Each extension can have voicemail, protected by its Voicemail PIN. Messages are listed under PBX → Voicemail.
Forward an extension's calls to another number — always, when busy, or when unanswered — under PBX → Call Forwarding.
Go to PBX → Recordings → Recording Settings → Configure to record inbound calls, outbound calls, or both. Recordings are listed on the same page.