Unauthorised cash withdrawal, watch out.

It is virtually impossible to contact Amazon(what kind of "Customer Service" is that exactly?. So I noticed £79 had been taken form my bank card which I did not authorise and I was most unhappy. I checked online and it seems the payment was for "Prime" membership. I know very little about Prime and from what I now know I have no interest in it. I had at no time allowed them to keep records of my bank card details either yet they had 2 of my cards recorded, which I duly deleted. I remembered I had made an order about 2 weeks ago which offered me "free next day delivery" though "Prime". There seemed to be little to lose as it was free and I was going to get my parcel quicker but I can only assume now as there appears to be no easy way to contact Amazon, that by agreeing to this I agreed to join Prime and to the money being taken from my account. I do not believe this is not enough agreement in Law to take a payment but I doubt I am going to take them to court and I think by cancelling my membership online I will get a refund but I am sure it's pretty sharp practice on Amazon's part. So as a low Amazon user I am fairly sure I can live my life without them and also that I can live my life without a company that takes unauthorised monies form my Bank account, especially at a time of year when money tends to be tight (Christmas) but I did feel strongly enough about this that I wanted to tell them and others what happened, so they can be aware and take care when dealing with these people, if you absolutely have to that is.