You can cancel your subscription for paid account at any time. In order to do it, you should go to your Ecwid Control Panel → click on your name in the upper right corner → Billing and Plans page and click the "Switch" link next to Free plan on the plans list. The loss of premium features is immediate.
Note that if your catalog size exceeds the limitation of Free plan, you will need first to remove extra products from your Ecwid store and then press the "Switch" link. After that the downgrade will take immediate effect.
We do not provide refunds for paid accounts. They're NON-REFUNDABLE.
Ecwid has free accounts with no time limits. They have all the features necessary to run a web store. We believe they are enough to check if Ecwid suits your needs and if you need a paid account.