If you paid for 12 months up front, you received a discounted price and your subscription ends after 12 months. You must then renew for another 12 months.
If you chose monthly payments you paid a little more for the subscription but the subscription does not end unless you cancel or default on payment. You must continue the subscription for 12 consecutive months in order to keep Sonar. After the initial 12 months monthly payment goes up to $19.95 a month. But you can cancel anytime after the initial 12 months and keep everything up until you decide to cancel.
If you are on a monthly subscription it continues until you cancel.
That was how it was initially explained.