3rd last Debit order not going through

I placed an order with the payment of option of 3 months, Payflex always debit my account the last payment didn't go through. I don't know what happened because I tried to contact them. My account had more than enough money for the last debit to go through. Every week I'm incurring R125 more debt to pay. I have been logging ticket so many times, they tried to call me once I didn't hear the phone and sent them my other number but still they didn't call back. Customer service sucks a lot, why can't we have a number to call because clearly they can't attend to the high demand of queries. It's better you call and hold or have a WhatsApp system that can assist. I'm waiting for some to call me; I will print bank statement and send it for proof that money has always been in the account. I have received 6 emails saying my ticket it's closed.