Why has £595 just gone missing?

I am really upset today, csa don’t seem to have a clue what they are doing.

I have a deduction of earnings attached to my ex partner. He’s in arrears so was paying about £460 a month. His payment in may though was only £320 as he’d not earned as much that month for some reason, but the employer has to meet the short fall the following month. So his salary in may he actually earned a lot more and they ended up deducted £595.

My ex asked if he could bring the rates down and spread them over a longer period of time which I arranged with csa but that was after the £595 had been deducted. The new schedule is in place so they have only taken £350 today which they have until the 19th of next month to pay. But this week I should of received last months payment of £595 but somehow it’s like it’s never existed. A lady from csa have said they haven’t received it and the employer have said they never deducted it and the next payment is the one deducted today, but that’s on the new schedule, she’s not looking at the old one, the new one wasn’t put into place until after the £595 had been deducted. I’ve spoken to the employer who said yes they did deduct it and it’s been sent. My ex even has proof it was taken on his payslip. So I phoned csa up again and this time spoke to a gentleman who said yes that payment of £595 is due so he’ll message the financial team at csa… so where is my money as the lady from csa has lied and made out that it doesn’t exist. How do I get my money? Surely we have rights?