The Free Trial Module/Plugin is not a real plugin or module, it's more of a process of how you can provide free trials to your prospective clients.
Offering Free Trial accounts is crucial when you are just starting out. It would be very hard for you to generate your first 20 clients, simply because no body knows you. You have no testimonials. People will always "doubt" your new services.
What you need to do is get some 20 clients or so and perform an excellent service to all of them so that they will sincerely provide their testimonials about your service.
Once you're able to put up some 20 testimonials on your website, generating more clients will be much more easier.
Okay let's get started.
As you would create any other hosting plan, create a new hosting plan in WHMCS and make it free.
Then download these two files which you need to run every day using cron job:
Change /path/to/your/whmcs/ to the location of your WHMCS installation directory
remindtrial.php will send out reminder to your free trial account holder reminding them that the account will self destruct in x more days and guiding them how they can upgrade their account into a paid one.
removetrial.php will simply insert the free trial accounts into WHMCS cancellation requests which will be terminated "immediately" when the next WHMCS cron runs. So all the trial accounts will self terminate.
Edit those two files and enter in your own preferences into the php codes.
Important note, as this is a hard coded file, you need to edit this line:
$sql_gettrial = "select id from tblhosting where DATEDIFF(now(),regdate)=$trial_period_days and (packageid=16 or packageid=17)";
See the packageid=xx or packageid=xx, simply replace that with YOUR OWN hosting package ID which you can see from WHMCS by hovering your mouse over the "Edit" product details, you will see the package id or product id of your trial products.
If you have any problems doing this, send us a support ticket and we'll help you out.