Mediazenn.com Put unauthorized charge onto my bank account.

I found an unauthorized charge on my bank account for, first, $1.00, then the next month for $39.99.  When I called the telephone number given by my bank, they said the charge was for "searching for a book or media" -- not even buying anything! 

They agreed to refund the charge "since it was within the 7-day cancellation period".  The refund code they gave me was C879-D337. 

I asked how it happened.  They said I might have "accidentally clicked on their site when I was looking at something else on the internet.  

I asked how they got my bank information -- they said it might have been with an autofill function, and advised me to cancel that function.  (I have no such function that I am aware of.)  I am awaiting the refund.