Nokia Lumia :: Incoming Call Shows Incorrect Contact?

Our office recently bought a handful of the Nokia Lumia 880 phones for our "out of office" staff. These phones have all been updated to the latest versions of the software/firmware using Zune on a desktop.

There still appears to be a problem with incoming calls showing the incorrect contact. It appears to be ignoring the first 4 digits of the phone number and only matches the last part. We live in Australia and have to mobile syntax of 04 XXXX XXXX. Numbers saved in the phone are saved without spaces like: 0401234567

Here's an example of how to repeat the bug.

Say this is a friends number: 0450100200 and you have that saved in your phone as Friend 1

If you have a second friend with a similar number on a different network like: 0417100200 and Friend 2 calls you, the contact name for Friend 1 will appear on the call screen.

We tested this theory by adding my number into the phone as a brand new contact, but we changed the first few digits of the number. My phone number was not originally in the phone, but when I called, my name appeared on the screen, even though the number saved was different to my actual number.

I don't know whether anyone else has this issue, but I would like to get it resolved. It seems sloppy design for the numbers to be loosly matched like this.