P900 SMS

Can anyone tell me why the following behaviour occurs, and more importantly,
how to correct it? Depending on how I select the recipient of the message
the displayed 'from' field varies when I view the messages in the 'Sent'
folder. If I select the recipient from my address book then the number
appears rather than the name of the recipient. If I select to 'reply' to a
previously received message then as long as that number is associated with a
name in my address book then the name is displayed.

Surely, if the number is in the address book then it would make sense to
always display the name rather than the number.

Regards

AC