On your phone select Preferences then Ringtone. Set Ringtone to Bell C. This will disable your phone's User Preference Ringtone and the phone will now use the configuration ringtones.
Using OBi Expert change the default ring for one of your trunks:
Voice Services -> SPx Service -> X_DefaultRing: 3
3 = double ring
Thanks!
This solved my question...
One point to add...
You can also change X_RingProfile: A or B and X_DefaultRing:1-10
I don't know what each number means. Maybe someone has a table they can share!