It looks like querying Task 'phone' is NOT supported. Can anyone confirm?
I can get Owner.Phone, but not read the phone field itself.
Acc. to this doc:
Phone Phone number of the contact or lead associated with the task. This field is automatically filled in with the value from the corresponding contact or lead record.
Please halp.
The contactId field on the Campaign member is not updateable. I don't think this has changed recently. You can check this yourself on your own org with the use of the workbench(enter link description here) connect the work bench to your org then view the standard object metadata for CampaignMember.
There's a table called the "Name" object. Fields that can reference more than one object, including Owner fields, Who and What on task/events, and other types of fields might be "name pointing." This facilitates the ability to reference multiple objects, but limits what you can do with queries. If you're not sure, run a Describe on a field and see if "isNamePointing" is true. You can access all the fields of the "Name" object, but no others are available by default. There's a feature in pilot (since version 26... sigh) called TYPEOF under the Understanding Polymorphic Keys documentation. You can request it for developer accounts (and only developer accounts, as far as I can tell) that changes those polymorphic name fields into something a bit more palatable. You won't be using it in your ISV project for some time yet, though, apparently.
Best Answer
You might try using the WhoId's relationship (Who.) to get to it.