Health Sciences Institute Unauthorized credit card charge of $37.00 Frederick Maryland

I logged on to my bank account and discovered a charge I did not recognize. I googled the information provided and discovered that I had been charged $37.00 by Health Science Institute.  Almost one year ago I made ONE purchase from them and promptly un-subscribed.  Now they decide to charge me without my consent?  I have found their contact email and sent a request for refund. Monday I will contact the Maryland Attorney General's office and report them for this kind of activity. By simply googling their name, I see that I am only one of many who have suffered this abuse. It needs to be stopped!