I've been Emailing Mark a few time because I was having the same trouble.
I just want to check with you and see if you're getting the same symptoms. The only time I would get the new phone # message is when the dialin failed for some reason. Not ALL failed dialins would cause the message, but all messages were on failed dialins.
Just as I noticed this connection and was going to try figuring out which error codes on the dialins caused the message I stopped getting failed dialins. I think it was something flakey on the number I was dialing in at, and only on my 3030. I got FAR fewer failed dialins on my 2020 using the same access #.
Anyway, see if you can notice any pattern connecting the message with a failed dialin and if so note the error message, and any error code listed in that message. Forward this to Mark and maybe we can help him track this down.
Mark, I hope this will help you find the problem and didn't post this to step on any toes, especially yours.