What steps do I need to take to cancel my work permit and extension of stay on a non-B visa in Thailand?

The user is seeking advice on how to handle the cancellation of their work permit (WP) and extension of stay related to their non-B visa, as they are not continuing with their current BOI company. Commenters suggest visiting the appropriate immigration office, particularly the Cham Churi Square One Stop Service Center in Bangkok, and bringing termination documentation to cancel both the work permit and visa extension.