Calico Cali Designs

I keep getting the following error, I do actually have free items on my site, that I want people to be able to "purchase" so I have the price set at 0. How can I avoid this error so that the free sales go through? TIMESTAMP -> 2013-11-20T13:38:20Z L_ERRORCODE0 -> 10525 L_SHORTMESSAGE0 -> Invalid Data L_LONGMESSAGE0 -> This transaction cannot be processed. The amount to be charged is zero. L_SEVERITYCODE0 -> Error thanks, Kat

Is there a tutorial on how to use the newsletter module? I'm a new user and I have all of the same questions as above. Please advise. Thanks!