No. Currently there is no way to cancel a license, once both sides have agreed on terms. Since there are multiple steps needed from both sides, to accept and come to an agreement, during each of which each side has the option to cancel, a cancellation after the fact is currently not being offered.
If - for some reason - a cancellation is necessary after all, both sides have to agree to a cancellation and get in touch with our help centre individually to let us know.