When you purchase McAfee, you automatically agree to the automatic renewal every year - it's stated in the T&C you can view presented to you prior to making the actual purchase.
You can always get Customer Service to disable it - contact them by e-mail, phone, chat, whatever you prefer.
No idea about the increase in price. Difference in price between a 1 User and a 3 User subscription? I suggest contacting CS.
//Edit: If I remember correctly, there's a 30-day no questions asked refund thingy. Which is 60 days if it concerns a renewal.