Amazon order canclation

I purchased an office software on Amazon from a third party named as media sellor. I placed order last night and regret today, then try to cancle the order. The order status is "they are shipping now", the canclation is not garanteed.  They said I can refuse for deliver or return for refund.

Does anybody here know what will happen if I refuse to accept? how much refund can I get. Are there any risk that I could not get any refund at the same time that the software was returned?

Thanks a lot.