I fear that I'm not fully able to explain but, are you sure that the changing of the loan rate, in a variable-rate loan, is right?
Could you simulate an already exists loan with a variable rate by yourself and after have committed 2 payments, change the rate and check it?

e.g.
open since 15/03/2009 (dd/mm/yyyy)
first payment 01/04/2009, every 1 month
change rate every 3 month, the 1° of March, June, September and December
So, the payment of 01/07/2009 have the rate changed.

Thanks for the help and sorry for my english.