https://support.google.com/google-workspace-individual/answe... (for individual) https://support.google.com/drive/answer/2736362?hl=en (for Drive) - I don't see it for Admin but it's probably the same.
Here's one for Google Workspace Admin: "The Annual Plan charges you for the exact number of licenses you signed up for through a yearly commitment." The "commitment" makes it sound non-refundable. https://support.google.com/a/answer/1230658?hl=en