Delete a sender by phone number.

Deletes a sender phone number from the account.

• If the account does not use parent/child accounts, the API ignores child_account_id and deletes the sender from the authenticated account.
• If the account is a parent account and you omit child_account_id, the API deletes the sender from the parent account.
• If you provide child_account_id, the API deletes the sender from that child account.