eFax try efax 30 days for free! but after 5 months i saw my unwanted (and unknow) monthly bill of 13,5 (70 tot), Internet

First: i search for a free service - to send fax by web. I saw efax.com: they say: Try for free for 30 days. In registering you need to write your credit card detail (they write for: avoid fraudulent you of the service....) I used probably the first and only time in september 2011.  Only one time.

Today, 4 apr 2012, I saw my credit card detail. I payed 13,5 monthly for this service (that I never used).  I try to understand why i don't see this detail when i subscribed this service. It is very hard and not clear that you'll have an automated debit in your credit card after 30 days! You need to read all the contract to understand this part. 

Dishonest! Excuse for my english - i'm italian