asterisk users - Apr 2007 - SNOM and Got SUBSCRIBE for extensions without hint. Please add hint to *8 in context inbound_sip

Hi,
I have an Asterisk 1.2.9.1 box and a bunch of snom phones.
I sometimes get this error:
*ERROR[31201] chan_sip.c: Got SUBSCRIBE for extensions without hint. 
Please add hint to *8 in context inbound_sip*
It seems that my SIP phone is sending subscribe command for numbers not 
inserted inside the snom function keys (and *8 surely is not). I 
searched on internet and Snom documentation but found nothing to avoid 
the Snom to send this commands.
Is there anybody who knows how to?


TIA

Giorgio