Returning calls to voicemail numbers

we have * and a number of snom phones.

when someone leaves a vm for an extension the phone receives a notification.

if you hit the vm button on the snom phone, it tries to call the number that left the voicemail with the phone (my understanding of this is that * itself actually leaves the msg).

however the vm button doesn’t know what to call, because * isn’t passing it a sip number to call to retreive the vm’s.

can anyone help:?: