The phrase should imply they will call you back — not that you desperately hope they’ll call you. And whatever phrase you choose to use, make sure it sounds like something you’d naturally say so you can deliver it with a confident tone.
It is important that you monitor your performance indicators for you to check if the slightest of changes can bring a difference to how many voicemails are received.

Users often don’t invest enough time into their messages, resulting in incomplete, unprofessional, or otherwise under-whelming greetings. Sure, crafting a greeting doesn’t sound all that complicated; however, there are a number of pitfalls users can fall into—i.e. informality, terseness, sincerity, lack of direction, and more. While none of these sound too catastrophic, they are often interrelated. As such, they tend to worsen any problem. For example, humor can cause informality, worsen ambiguity, and weaken sincerity. That being said, users should strive to avoid ALL these pitfalls.
Congratulations! You've recorded a professional voicemail greeting that your callers love. If you want them to keep loving it, you'll need to update regularly. Adding seasonal information and varying your message keeps your greetings fresh, which is especially important for businesses whose clients and customers call in on a regular basis.