Hi and a Warm Welcome to the forum.
Here is a help link which may be of help ->
http://support.vodafone.co.uk/Calls-texts-and-voicemail/Voicemail/50540599/I-can-t-switch-my-voicema...We have heard of people having issues with porting but that's usually that it's taking longer than usual.
Try turning the phone off and on and if you can try an alternative phone with your sim in to see if the short codes work.
How "recently" did you port as it may just be settling.
If this persists then please do contact Vodaphone via 191 or use Live Chat available through the Contact us link at the foot of the forum.
Current Phone >
Samsung Galaxy s²³ Ultra 512gb Phantom Black.