- Go to the dial screen on your IPhone and dial the following code and then press CALL button
I'm using Celcom as my network provider so my Voicemail number is 1313:
*5005*86*1313#
Once you've press CALL button it will set your Voicemail number into iPhone memory. So next time to hear your Voicemail message you just need to click on Phone Icon ---> Voicemail button and it will auto-dial your voicemail number.