you can cancel an order at anytime . After the run starts its up to the seller if he or she wishes to refund . Its not a good idea to frequently refund as it then gets listed your percentage of refunds and all sellers can see this when you submit the order
Martin, when placing an order, you have to select the date when the seller has to start delivery. The seller will not be able to start delivery later than on the scheduled date. The seller also cannot change the delivery start date.
Please check the tutorial https://udimi.com/help/buyer/how-to-buy/6
Every solo ad must be delivered within 100 hours, or it will be refunded by the system.
Contact Udimi support via the Help section so we could further assist you.
You can also ask the seller if he can start earlier. Unless you placed the order with the "No early start allowed" option (I guess you didn't) the seller can start even immediately.