To downgrade to a free plan, please navigate to the console here: https://console.temasys.io.
Under Manage Apps, click on the App for which you'd like to downgrade your plan and choose the "App:Billing" tab.
You can then click on the 'Downgrade to Free Plan' option at the bottom of the page.
Please feel welcome to reach out to us at userhelp@temasys.io, should you have any queries about a trial extension, billing or a custom plan for your unique needs.
You may also wish to refer to our article on What are the features of the post-trial free plan?