To cancel your VPS with Name.com, you will simply need to let the product expire. Your VPS shows in your Name.com account, which is where you can renew the product, plus, enable or disable automatic billing. If you do not wish to renew the product, simply ensure automatic billing is disabled and, when the product expires, it will be removed from your account. No action is required by you! We'll take it from there.
If, for whatever reason, you would like to have your server deleted or removed, please contact email@example.com and request it be deleted. It may be a better idea, however, to simply shutdown your server from your VPS Control Panel and wait for it to expire and be removed. That way, if you change your mind prior to expiration, you can simply start the server up and be back online.