I have noticed the past few days, usually on off peak times for longer connection that the UML290 will connect without VZAM running. I am running W7 Home Premium and the latest software/firmware updates. I first noticed this last night when I started the desktop and the network icon showed connected with Internet access and worked for several hours but since then it is flakey at best most of the time. As a mater of fact I had to switch to another connection to complete this post. Point being I connected to VZW network from bootup without Access Manager running. I did notice PTUML290 Connection Manager Service was running and Network sharing center showed the UML290 connection connected with internet access.
This happens to me as well sometimes. I'm not sure the exact setting in W7 to stop that, it's in W7 for sure, not the modem doing it. I will connect to VZAM and it will disconnect it and use the VZAM from there. You can always go to your Task Manager and stop it if you want.
VZAM sometimes does not unload properly, so it's running even if you don't see it. You may see one (or even two) instances of the process in the Task Mgr. You can kill it and restart it. One reason it takes time to start and stop is that it has to wait for Wireless Zero Config service to stop so it can take control of WiFi connections. When it exits, is usually restarts WZC service.
You can also set yoru VZAM prefs for manual startup of the program and connections. In this case if a connection is lost, you may have to manually re-connect.