Stamps.com is a rip-off Inglewood California

Stamps.com sent me a packet in the mail offering a free trial. I downloaded the software and used it once. Somehow I ended up with $15.99/month charges with no idea at all of what I'm supposed to get for those fees.  This is now the third cycle and I'm waking up to what's going on. I logged into my on-line account today (Sunday) and tried to cancel the account, but you can nly cancel the account by calling them M-F.  I will call tomorrow and will cancel, and will also try to get a refund. I don't recall signing up for this. I presume I was askd to enter my credit card information in case I wanted to purchase more postage, but I do not at all recall authorizing it fro monthly fee.  That would make no sense for me, a small user.