The easiest way to check voicemail remotely is by using the Cloud Softphone app on your smartphone. Checking voicemail is easy on that app, please see this article. https://intelafone.desk.com/customer/portal/articles/1344976-checking-voicemail-from-a-smart-phone
If you do not have access to a smartphone you can check your voicemail by dialing your number. As soon as the unavailable voicemail message begins to play dial * and enter your voicemail password.
You will need to first setup a password on your voicemail by dialing *123 from your Intelafone device then dialing 0, then 5. Then enter your password, and enter it again to confirm. Follow the prompts to complete the setup process.