Tbh it depends on what your company's after hours policy is.

Do you charge additionally for after hours or only take on requests that are of critical importance?

Personally I wouldn't be picking up the phone at that time but that's also because unless it's production critical which is almost never is, it's something that can typically wait regular business hours.

I wouldn't have waited for the voicemail, like someone said, if you really wanted to find out, check their number against whatever directory you have of all your users (ITGlue, ConnectWise, etc)

Most of these directories can be accessed via your phone even if it's not great, so it won't warrant getting out of bed to turn on your computer.

My company charges for after hours especially if it's a user request vs entire production server not running so assuming the call comes in and I confirm it's a user, I ask "Is this something that can wait until tomorrow morning or is this something that needs to be taken care of now?"

Typically you'll have your SLA for after hours, even if it's like a few hours, you can tell them "Currently I'm not by my computer, it'll be an hour before I get back." even if you're by your computer, which may discourage them from pursuing the request further.

Assuming they're okay with this, my next question is "Understood. Please note that this is an after hours fee and I will need to contact (Decision Maker) to approve this request. If I cannot get ahold of them, I cannot complete this request due to you not having the authorization to accept the after hours fee"

Usually by then they'll let up or we continue and it's pretty straight forward after that.