Ideally, a business should have a complete set of messages for every phase of their call flow from beginning to end. While voicemail greetings are an important part of the phone system, there need to be recordings for everything leading up to the voicemail as well (assuming there are other steps in the call flow).
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.

The difference is subtle and primarily reflected in how we choose to deliver pre recorded phone calls to our customer's contacts. When you think about phone dialers, you’re talking about a service that makes phone calls to connect someone to a live person - typically for the purpose of selling or qualifying a lead.
A secretary in a doctor’s office creates a voicemail greeting that says, “If you have a scheduled meeting with us, we could use copies of all your medical documents from last year, so come prepared.” Using the word “could” gives patients the impression that they don’t necessarily “need” last year’s documents. See the difference between “could” and “need”? Your word choice can impact a future meeting significantly. If you want a customer to perform a specific action, you need to pay close attention to how you express your calls-to-action.