Change number of rings before voicemail kicks in?

Is it possible to change the number of rings before voicemail kicks in?
Thanks

jetskidia
I asked Lebara and they sent me this, which doesn’t work?
Standard Voicemail Divert Off: 1210
Standard Voicemail Divert On: 1211
Access Voicemail Services: 121
Extend Voicemail Timer: **61*121*10*30# or **61*121*11*30# (Both should be tested) - Timer can be set to : 5,10,15,20,25 or 30.

Anyone?