I'm trying to turn of voicemail

[KateBee46]

I have the same problem.

I'm trying to turn of voicemail by sending VM OFF to 150 but it won't send from abroad 

[Plymouthbloke1]

Just dial ##002# from your phone keypad. That should clear diverts.

[bristolian]

The solution above will work, providing the reason for "won't send from abroad" is not a lack of roaming.

If it is - then your phone won't be able to connect to any foreign networks or thus perform any network-reliant functions.