Swaps a target's primary number with a new one.

• If a specific number is provided (type: 'provided_number'), the target’s primary number is swapped with that number. The provided number must be available in the company’s reserved pool,
  and the reserve_pool experiment must be enabled for the company.
• If an area code is provided (type: 'area_code'), an available number from that area code is assigned.
• If neither is provided (type: 'auto'), a number is automatically assigned — first from the company’s reserved pool (if available), otherwise from the target’s office area code. If no type is specified, 'auto' is used by default.

Rate limit: 1200 per minute.