how to use daloradius to limit pptp users time?

hi, all I am trying to set a test billing plan where the user 1 minute total. It's not quite working and I have a few questions: 1. First I set up a billing plan called "1time": Billing>Plans>New Plan. I set Time Settings>Plan Type = Accumulative, and Plan Time Bank = 60. Then I assigned the plan to a user. Billing>POS>Edit User>Plan Name = "1time". But after the users over 1 minute, and then logs off, they can still log back in. It seems the Billing Plan does not stop the user from logging in. What should I do such that the user gets blocked after 1 minute? daloradius:version 0.9-8-SVN freeradius:version 1.1.6 Thanks!