You can cancel your order as long as it has not been packed yet. You can find the order status in your customer account under "Orders".
To cancel an order, click on "Order details" for the order, where you will find the option "Cancel order". This option doesn't appear anymore the order has been packed and sent out.
If you paid by credit card, TWINT or PostFinance, the reserved amount will be released again.
If an order is cancelled the associated Cumulus coupons are deactivated. If you would like to use these coupons again, simply activate them once more.