psigate change

I have PSIGate set up as a payment processor. As far as i know the code im using and all works fine. I need a change done. i am using this module [login to view URL] i need trial put in. right now it charges the amount each month i need the following put in and made working my my system example user joins. pays 7.50 for the first month pays 39.99 each month after this should be a very simple job.