You can downgrade your plan to a Non-member under the Plan menu on your Pixc dashboard. Just login to your Pixc dashboard and click Plans, then click the Change Plan button.
Please note that downgrading your plan takes effect at the end of your current service period. If your subscription starts at the 5th of the month, and you decides to downgrade on the 15th, your account will officially get downgraded to Non-member on the following 5th of the month.
At that point, you will forfeit your access to features included in the Member plan even, including your credit purchases.