Conditional Fields, being weird

I have a custom registration form with a Role select (I tried Dropdown and Radio) radio.
It’s just a basic phone number field, for now.

I have it set to :
show – Roles (Radio) – equals to – um_both
show – Roles (Radio) – equals to – um_advertiser
hide – Roles (Radio) – equals to – um_affiliate

(I’ve checked the source, the ID’s match)
So, what should happen is if I select Both or Advertiser from the radio options, the telephone field should show. If i select “Affiliate” then it won’t show (as default).
Now, what happens is the field (Phone Number) is showing when the form loads (It shouldn’t be).
Choose Advertiser : Phone number dissapears
Choose Affiliate : Phone number dissapears
Choose Both : Phone number dissapears

Am i doing something really daft?