If you create or import a contact or company it is allocated to your current team, how can you change the team setting on a contact or company so it is visible to another team?
The HubSpot Team or Contact Owner Property (if you want to assign the Contact to a member of a particular team) can be edited in bulk as per this Knowledge Base article, if you want to edit a list. This should override any team assignments they pick up when imported and reassign the Contacts.