When I was in my 20s, I had an answering machine with a 30 second outgoing message tape. I thought it would be fun to come up with all sorts of cute or funny messages for my friends to hear just before the beep. It got pretty elaborate sometimes, with celebrity impersonations and movie spoofs and other things. I didn't usually get many important phone calls anyway, so I didn't see any harm in being funny for the few people who did call.
16. Hi, you’ve reached [X Business Name]. Our regular business hours are [State opening hours]. If you need to reach someone immediately, please call [contact’s name] at [cell phone number]. If not, leave your name and contact information and a representative will get back to you when we re-open.

Begin by letting the customer know that you’re sorry that you missed their calls. Tell them your company name, department and beseech them to leave a text. Today, people are very allergic to scam and fly-by-night telemarketers. Greet your potential clients and tell them exactly who you are if you want them to leave their messages in the tone.
You might also consider giving them the option to skip your voicemail message completely by pressing another key (again, check with IT). You also want to make callers aware what you will return their call, instead of telling them that you will try to return their call--and let them know when you are likely to do it, if possible. If necessary, provide additional or emergency information in your voicemail greetings. My dentist, for example, lists his cell phone number for emergencies.