Just don't set user bandwidth daily/weekly/monthly.
As of yet PF doesn't send the traffic data correctly. 50Mb could be counted as over 200 MB. BAndwidthD seems to be just as bad off.
But using freeradius2 to limit speed works fine right now.
Please don't mix up different things. The fact you are talking about is limit the amount of traffic. You want to stop access after a user downloaded 500MB. This is not related to that topic!
What he is talking about is bandwidth limitation. He wants that a user is always having 2MBit/s download and 1MBit/s upload but another user should have different limitations!