Am I entitled to supplicate against and blame a customer who backed out of purchasing goods for which I incurred debt to buy, and am I wronged by that?

It is not permissible to sell a commodity before possessing and acquiring it, because the Prophet, peace and blessings be upon him, said: "Do not sell what you do not have." What is issued by the customer is considered a legally binding promise for him according to some jurists, and this entails bearing the actual damage if he withdraws from the purchase. It is permissible to supplicate against one who has wronged you, to the extent of the injustice.