Caller Id - Greyed Out

Hi,
I have recently moved to another country and am experiencing difficulties making calls on my phone.
The network provider tested my sim in their phone and it worked.
It appears to be a setting which hides the caller id for outgoing calls.
If i go to:
Phone>Settings>Call Settings>Additional Settings
I find 'Caller Id' however this is greyed out.

Any idea what is causing it to be greyed out?
And how i can resolve it?

I appreciate any assistance offered.

Many thanks

Ben

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