Craft 5 - How to revert from Pro to Lite

[paul-frost]

As What3Words have removed the conversion of lat/lng coordinates to w3w from the free api and now require £7.99 month to enable it, I have no need for the Pro version.
How can I revert back to the Lite version?

I want to do this as I’m still seeing a w3w data field but can’t manually add anything to it, and it’s confusing my users. I have disabled it in the field settings but the w3w field still shows.