I ordered a book from amazon and found that I'd also been signed up to prime at about £8 a month automatically.
Sign out of prime not obvious but possible
I dumped them forever after being caught like this. They refunded me immediately, but it left a nasty taste in my mouth. :grumpy:
I had emails within a week before I was to be charged. There is also a little box you can uncheck to not automatically subscribe. Been using Amazon for years with very few problems. The only thing I do differently now is pay monthly and can cancel any time. It means I don't get weekend delivery but I get free next day weekday delivery.
There again, I have never used ebay.
It's whatever you are comfortable with.