splitting personal allowance

I have been receiving a pension since 2018 and started working again in 2020, my personal allowance has been split so that I pay a minute amount of tax on my pension. However, I noticed on my recently tax code notice that my pension was not included so got that corrected. However, the whole tax allowance is being applied to my employment and I want to change it back to the way it was, is there a form for this? I dont particularly want to go through the rigmarole of calling as I was on the phone on 4 separate occasions just trying to get it fixed in the first place

Hi
You would need to call or request this in writing :
Income Tax: general enquiries
Thankyou.