How can I try the Free PBX software?
We assume you mean the free version of the SARK ".iso" and not "FreePBX" (which we most certainly can't help you with

)
To be honest, you already have it. The .iso is little more than sme server with sail and asterisk included. The "free" version is identical to the commercial version, the only difference being that we support the commercial version (and the free version has "UNSUPPORTED DEVELOPER RELEASE" plastered all over the splash screen).
However, if you're still interested or you want to offer SARK/SAIL to your customers (with support from us) then drop us a line at admin@selintra.com
Kind Regards
Selintra