Post Tax return filling tax code changed and again when I called HMRC, it changed back to 1257L

Hi, I applied for tax return and in result my tax code was updated by employer based on input from HMRC( from 1257L to 3254L). It was taking bit delay in refund so I called HMRC contact centre and I was told my refund amount has been drastically decreased and tax code was updated back to 1257L from 3254L. May I know why this happened? In the return it was showing refund of 5k now it changed to 1k. Another query is will I have to pay back the extra tax for 2 months when my tax code was 3254L?

Hi sanjh,
We are unable to check personal records via the forum.
You would need to contact HMRC to discuss your queryhere:
Income Tax: general enquiries
Thank you.