How can I add a customer's phone number to a packing slip?

When customers checkout using the “local delivery” method, they are required to enter a phone number. This phone number appears on the order page (that I can see) under “delivery instructions”. This phone number is not appearing on the packing slip. When I add special delivery instructions to an order, the text is being displayed but the phone number that’s being populated into that area is not.

Does anyone know how I would access this to add to a packing slip? Note that it is not shown in {{ delivery_method.instructions }}.