Please assist with exstra charges and to correct my pin

I contacted payjustnow to tell them that i can not make a payment because they keep on saying my pin is incorrect they said i must take a selfie change the pin logged out and in again i did all the above but still nothing is happening i have sent them emails chat to them with no help now they debited my account and there was no money now everytime they debit theres a huge fee that they put in with the amount that you owe them that will make impossible to pay of your debt by them in future because of all these ridiciolus charges please assit i never skipped a payment only when they updated the app i started hav8ng issues