Change of deduction date

I took a car finance,provided with all relevant documents,my deduction date was captured as 25th of each month and I have advised that my salary date is on the 27th of each month. They said they will change it. Till this date they haven’t. I provided with proof of employment that also confirms my salary date. First instalment went off last month of which the 27th was on a holiday. “27April 2025” hence it went off. But now 27th May 2025 is not on a holiday so I won’t get paid earlier. I don’t know why is it difficult for them to just change my date.