having the same prob with E71.
its got something to do with the how the phone's firmware recognize length of the phone number. if the number is saved with the area/country code, caller name is not presented but is shown in SMS and vice versa if no area/country code is saved.
i'm also trying to fix this prob. my operator also have 7 digit numbers
In my experience the contact display always works , using 12 digits .
(+49123456789) . Except :
1) when the Network / Operator doesn't support number display : ask your operator
2) when the caller disables his/her number display : ask your contact .
SMS always come with a number .