Incorrect debit order date messing up my acc

I just realised that for the past 4 months, my Virgin Active debit orders have been returned unpaid due to insufficient funds. Further to that they have attempted to debit my account at least x2 every month. Reversals which attract a charge of R137 a transactions and are affecting my bank account negatively.

My debit order mandate with Virgin Active is on the 25th of the month (my payday), and so are all my other debit orders. Reason for that is because I know that after the 26th I do not have any funds on my account. Virgin Active has been randomly debiting my account, anyday of the month and not on the agreed date.