Visual Voicemail is provided by your cellular service provider. Contact them and ask them to enable Visual Voicemail on your line. (The Sunbeam F1 works with the Verizon and T-Mobile VVM system, but not with AT&T).
If you have recently swapped the sim card or switched to a different carrier, you will need to reset the phone to connect to the new carrier’s VVM system. First backup your data such as contacts, messages, etc. to a microSD card. Next reset the phone: System>settings>phone settings> BasicOS>reset options> Erase all Data>press Reset phone>the phone will turn off, reboot, and then erase all user data. After the reset is done, accept the visual voicemail terms and it will now show your voicemails.