Rather than ask who will do it... ask yourself... why would you want to offer free trials?
At least if you're charging a few bucks -- you'll probably cover your bandwith costs... but with free trials -- you're getting nothing. A huge majority of free trial signups will probably cancel within the 3 days (or whatever time period you're offering)... and those who don't cancel it -- will probably claim they didn't realize it was recurring - and the "free" was misleading
