When debit order is after a public holiday

I have a loan with Capfin I are not fair and clear as per their contract they state on the terms and conditions that if there's a holiday before your billing date they bill you before , where are they expecting us to get funds from 4 days , this morning 18/03 I received an SMS that I must fund my source Acc because they will be devoting today when my actual date is the 22nd. Capfin is messing up with our cheques account and I will be charged for unpaid debit order; and this is also affecting my credit status with my bank .