I attempted to modify a scheduled online payment by splitting it

the payment between two saved payment methods. I adjusted the amount for one method and kept the original date, then selected the "split payment" option and entered the information for the second payment method, including the amount and date. However, I keep receiving an error message stating that a payment is already scheduled for that date and to choose a different date. I cannot select another date as it would result in a loss of service. Can you provide guidance on how to resolve this issue? Thank you.