There is a *123 star code that allows you to record a new voicemail greeting.
http://www.obitalk.com/forum/index.php?topic=6736.0 shows the OBiTALK configuration required to enable the *123 star code.
Although I have used OBiTALK before, I either forgot the magic incantation or the website has changed. From the
OBi Dashboard, click on the
Home button just below
My OBi Devices. Scroll down and click on the
OBi Expert Configuration button, accept the prompt and then click on the
Enter OBi Expert button. Expand
Star Codes in the left navigator and select
Star Code Profile A. To set a new
Code30 value, I had to uncheck
ObiTALK Settings and then uncheck
Device Default.
When callers get to your voicemail, your greeting will be followed by an automated message '... when finished, press the # key'. The three options presented are replay, re-record and delete - I guess everyone just knows to hang up to save the voicemail. I added a few words to my voicemail greeting to clarify this.