Hi all can any body tell me howi can change the dafault auto attendant message

I think the default auto attendant greetings are User Prompts 5 and 6 .

You have to record a new prompt in wav format and then upload it to the ippbx in the prompt maintenance section with the filename;

v2820pbx_g711_userprompt05.wav for the office hours greeting
v2820pbx_g711_userprompt06.wav for the out of hours greeting.

You can use the Voice Prompt Utility to record;

http://www.draytek.co.uk/support/download/IPPBXVoicePromptUtility_1.1.2.zip