To clear any customers doubts or expectations, make sure to mention on your voicemail when you’ll be available. Don’t say that you will “try” to return their call. Instead, offer them a realistic timeframe in which they can expect their call to be returned, so they know what to expect - whether it will take you 24 hours or a week to get back to them. This will eliminate your customer’s worries about your timeliness and encourage them to wait for your reply instead of heading over to your competitors.
If you’re actively looking for a telecommuting gig, or you’re a small business owner looking to project a polished, professional image, do yourself a favor and call the number you’re giving out and listen to your voicemail greeting or, heaven forbid, see how your phone is answered by whatever family member happens to pick up the ringing phone. Are you impressed, or embarrassed? Was it useful, or was it a colossal waste of your time? Could you understand every word clearly, or did it sound like you were in a tent in the middle of a monsoon? Is the information you provided recent, or was it dreadfully out of date? Did it sound like someone you want to work with or hire? Or not?

From the Skype for Business desktop app (if you are running Click-2-Run build C2R 8201.1002 or later), select Set Up Voice Mail. From the voicemail email, click the Set Up Voice Mail hyperlink. On the Skype for Business Settings page, select Voicemail. On the Voicemail settings page, you can configure the following settings:
These are just a few ideas to get the gears turning. These are simple examples, but don’t be afraid to show a little personality.