How do you tracking hangups

[Justin Silverio]

How do you track your hang ups from your direct mail?

I was thinking about getting one phone line per lead type (i.e., absentee, tax lien, foreclosure, etc.) so I can better track my response rates. Anyone do this? And if so, what service do you use? Google Voice is not an option because I ran out of phones to have google voice forwarded to.