IPhone 5s - visual voicemail after 11.0.3 update

I have always been able to access visual voicemail and receive voicemail notifications when I was connected to WiFi.  Now I can only access visual voicemail and receive voicemail notifications if I'm connected via "cellular data".  I sometimes won't see a voicemail notification for 36 hours after it was left... very frustrating.  Does anyone know if there is a setting I can change to be able to access visual voicemail when connected via WiFi?  Any suggestions or help would be much appreciated!