Paid my account but was still debited

First the service is poor, the contact centre never answers the phone call also the watsapp agent takes 45min to respond to the massages. I paid my monthly payment and I keep on getting sms that my account is in arrears and I took time and send pop to their account .no response nothing. Today they have odesity to double my debit order.i am very angry. I need this rectified and my money paid back.