Divert when already overseas

[SarahF1]

This is my first post, so hope it’s in the right place.

I need to divert all my voice calls straight to voicemail but need to retain the ability to use WhatsApp on Wi-Fi.

I’m already in Mauritius and forgot to do it before I left.  The call rates are really expensive and need to do this asap.  Appreciate any advice including the full number for ‘901’.  Thank you

[MI5]

@SarahF1 

Any help here ?

Guide: All you need to know about O2 Voicemail 901