Strange message from Polycom soundpoints

Ive noticed that when your logged in to asterix -r, when someone picks up a Polycom phone (or hangs up) you get this;

Aug 31 11:32:20 NOTICE[16919]: chan_sip.c:9508 handle_request: Unknown SIP command ‘SERVICE’ from '192.168.2.53’
Aug 31 11:32:21 NOTICE[16919]: chan_sip.c:9508 handle_request: Unknown SIP command ‘SERVICE’ from ‘192.168.2.53’

Any idea why? Or how to stop it. Polycom wont reply about its unknown sip command…