I want my order canceled and have refund with payflex

I made an order,with payflex buying my children school uniform,but the machent has never received those funds,in which payflex deducted the first payment on my account and when I fone the machent,they did not receive the money,I tried calling with no.luckies.i send email after email no response from them. Such a terrible service. I'm.so.frustreted since the kids don't have winter school uniform,and it's now almost 3 weeks