Employer has not updated my tax code

I have been notified of a tax code change for 24/25, this was almost 2 months ago. My employer has changed the main part of my code but still has me on M1 and will not change. The new tax code in my personal account does not have the M1 against it. I've asked them several times about it but they will not correct it or ring the help line.

Hi,

The month 1 basis would have stopped at the end of the 2023 to 2024 tax year. If the employer has not yet changed it, you will need to contact our Income Tax team so we can issue another code to the employer to confirm to no longer use the month 1 code.

Income Tax: general enquiries

Thank you.