Nokia Mail powered by Yahoo - Why do I have duplicate contacts for my Nokia Mail?

When creating a new contact for the same or similar name, or updating an existing contact, if all the fields in the contact do not match, or are not a subset of the other, a duplicate contact is created - see below

Case 1:John D Doe, 770-555-1335John D Doe, 770-555-1335Exact match. Merged.Case 2:John D Doe, 770-555-1212John D Doe, 770-555-1335Phone numbers mismatch. Neither is a subset of the other. Duplicated.Case3:John D Doe, 770-555-1212John Doe, 770-555-1212Second is a subset of the first. Merged.Case 4:John D Doe, 770-555-1212John D Doe, 770-555-1212, 770-555-1335First is a subset of the second. Merged.

Case 5:John D Doe, 770-555-1212John Doe, 770-555-1212, 770-555-1335Neither matches a subset of the other. Duplicated.Case 6:John Doe, 770-555-1212John D Doe, 770-555-1212, 770-555-1335Everything in the first appears in the second. Merged.