Re: Deactivate Call Waiting
It is definitely possible to turn off call waiting. The setting is found in the user section of the PAP2-T, so it is easy to get to, and as I recall, it doesn't change when you reboot the adapter. I would ask support to do it, however, so that it's done right.
Getting inbound calls to go to "Busy" is a lot trickier. I'm not sure it can be done. Perhaps if you disable voicemail. There is a setting for "Do Not Disturb" which goes to Busy, but that's something that you would have to set each time you are on the phone, which is not practical. Inbound routing can send calls to Busy, but there is no way to define a group as "whoever calls when I am on the phone." I don't see any other choices.
Many people have asked for call routing based on "Busy" or "No answer" conditions. It would be great to have the option, when you are on a call, to have incoming calls be forwarded to a different number, go to voicemail, get a busy signal, etc. Unfortunately, that feature is not available with VOIPo.
Re: Deactivate Call Waiting
Based on the way our network is designed (with support multiple calls), it's not going to be possible to send the calls to busy when call waiting would kick in. If it's disabled, the calls would just go straight to voicemail or failover.
Re: Deactivate Call Waiting
If he could be certain of a failover condition by disabling call waiting and voicemail, could he then use the failover feature to forward the call? He might then be able to send the call to a number that plays a busy signal, or at least an acceptable recording (see http://moo.net/numbers.html, where you can find a number that says "all circuits are busy now.") Or possibly get a virtual number or a Google Voice number and set up a mailbox where the outgoing message is a busy signal?
I admit, this is something of a kludge, and turning off voicemail is not a great option.