Rain.co.za debit order incompitence

I changed my payment date to the 1st of the month. Then weeks later on the 22nd I get debited. I logged a complaint for their support to contact me, and still have received no response. Tell me why my previous payment date was the 25th but as soon as I change it I get debited ion the 22nd instead? Now I have banking fees to pay for the debit order that bounced. What on earth is going on?