Bad customer service and *****ulent ****ming penalty charges

Tuesday I woke up to sms notifications that payments didn't go through "Your PayJustNow payment failed. You have got today to ensure funds before late fees apply". Immediately I went on to the app and tried to pay manually which I got an error that said I must check that my card is valid. I called my bank Nedbank and they confirmed me that there's nothing wrong on their side, my card is valid, I have sufficient funds and no changes have been made to my limits, and I emailed them to inform them. Wednesday morning again I woke up to sms and email notifications that payments didn't go through still which I tried again to manually pay and got an error, soon after that I saw they added excessive charges to every purchase I have on my account. I called the bank again they confirmed the same and expressed that am not the first customer to call in about the same issue with PayJustNow. I have sent several emails with my contact numbers with hopes that they will call me back so we can sort this matter out as I tried to call them to no success, their contact center just rings to no answer. I am not prepared to pay penalty fees which was not my doing, if it means I must go pay physically at the stores I will do so as I feel this is a **** that payjustnow is running.