Yes, you can easily upgrade your account at any time. The cost is simply the price difference between the two plans. There are no other fees involved as you will only be charged the prorated difference between the original and new plan. The same goes for downgrading. However, we will not provide a refund for unused time, so we suggest you wait until the end of the payment term (around 5 days before your invoice is due) to submit the downgrade request.