Payflex ****med me

I payed my online order using payflex, my attempt to make payment was canceled due to delay in approving payment from my bank ,I then went to my basket I made second attempt to pay it was successful, I later realized that payflex has a orders other my profile ,I sent them emails and forwarded proof that the first order didn't go through it was canceled they refused to refund me and threatened to blacklist me if I stop paying them ,the amount I owe payflex is R3500 but they taking R8400 from my account. I'm being bul**** and ****med