In order to cancel your account all you need to do is head to 'Settings' then "Plans & billings". Once you're inside the billing page simply click on "Cancel account" in the bottom left corner.
You will still have access to your current subscription until the last day of your current billing cycle, so you can still publish ads and take part of the features you have paid for. Once the current billing cycle ends you'll be downgraded and your account will be dormant.
Please note that if you return to Qwaya in the future, all you need to do is update your subscription/billing and your account will be as you left it.
You can read more about canceling your subscription here.