Hello,
Why dont you create a new "Package" called for exemple "Trial Package" and then on "Princing", set the term 1 Month, on price leave it 0.00, and then check the option "Cancel at end of term".
Finally on the "Welcome Email" just put a message, for exemple:
Then if your client contact you, just edit the Client service to outher Paid Package
I hope, for now it helps you