There are 2 model numbers on my phone
On the larger label - KX-TG6641
On the smaller label with the S/N - KX-TG6643B
Phone is a couple of months old and this problem showed up very quickly.
YES, we do have another old phone system in a bedroom. I will test the old system.
You were right- the other system was actually ON and taking calls and the system was full. It didn't have a greeting so the new system greeting was being played. I turned the old system OFF and replugged in the new system. Then I called our number from my cell phone and it took my call recorded my message and there was no announcement from the old system. I think the problem is solved!