How long does account merge take?

My employer made an error when setting me up on their system in July. I have been on emergency taxsince then. In October an HMRC staff member identified this problem and started the merge process. I was told it would take a few weeks. It's been nearly 3 months. Every time I call for an update I get cut off after being on hold for 3-60 minutes. I am owed thousands of pounds now. I've had to use my savings to make up the shortfall and pay bills, and we basically had to cancel Christmas. I'm desperate to get some clarity. This is my life! There is no end in sight.

Hi,

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Income Tax: general enquiries

Thank you.