Access records, by role, problem of duplicity

 Hi, Right now I have a sales role, where the sales people have the ability to just see their records (the ones they are the owner).

But I have a problem, I already have a database of Accounts and Contacts or Leads, with owners and everything, but here I put an example of the problem I have:

Sales Person 1 only sees 3 contacts, because he is the owner of those 3 contacts. Later he wants to create a new contact (John Smith), so he creates it and he is happy with it.

Then the Administrator of the CRM, sees that there are 2 contacts duplicated (John Smith), but they have different owners (so the sales person 1 couldnt see because the permission he has, that it already existed; so he created a new one.