I bypassed the netzero software by putting email@example.com and my password in the Windows dialup network connection settings. If I used just my username or firstname.lastname@example.org, it didn't work. As an example, if your netzero username is shaggie, then you would use email@example.com in the dialup settings. shaggie or firstname.lastname@example.org wouldn't work.
Netzero changes the local phone access numbers occasionally and retires some of the existing ones. Their software would need to be used occasionally to see the latest functional local phone numbers.