You can solve this by creating 2 associated entities, one person entity and one entity with the phone number, that are associated like this:
While creating a ContactDetails object, make sure you set the association to the associated person:
Afterwards, you can retrieve all the phone numbers of a person by retrieving all associated ContactDetails objects of a person over association.
EDIT: Apparently my screenshots haven't been uploaded, so I'll explain it through text. You can create a 1..* (one-to-many) association between the person entity and the entity with the phone number attribute (I use ContactDetails for this example). While creating the ContactDetails object, make sure you set the ContactDetails_Person association to the associated Person object, and you should be good to go.