Do you mean ask blizzard to refund you for payments? - This used work before banwaves started, you could get preorders and sometimes key purchases refunded. Once they started with waves they started refusing this. Not saying its impossible now, it depends on gm. Do you mean contacting your credit card company?
I always do a CC chargeback when it's been < 6 mo, and it's worked each of the last 3 times (banwaves are sad!)