Payjustnow deducting default fee even though I paid within 24 hours

I set my payment date for the 27th since that is the date my salary is paid. I had forgotten I changed my bank card, and the payment was not able to go off on the 27th. I realized this when I received a notification from Payjustnow that my bank card details were incorrect when they tried deducting the funds. I changed the details and then did a manual payment on the 28th, within 24 hours. Their policy states that if you pay the instalment within 24 hours you will not be charged a default fee. I will still charged this fee and their support is ridiculous and arguing with me that they deduct early hours of the morning. My date for instalment is set to 27th, not 27th at 12 am, I made the payment on the 28th at 8:37 am as they informed me but not early enough according to them. Nowhere on their policies does it state that your payment is set for a certain date and time. 28th is still within 24 hours of the 27th, but I was still charged the default fee. Seems like a technicality to out people of their money.