HICBC High Income Child Benefit Charge charge and self assessment help

Hi, looking for any help like pretty much everyone else, never known of this type of penalty. I divorced from my ex in 2023, and as per the financial order this stated she would receive the child benefit for all 3 kids since 6/23. Unbeknown to me as I was still down as the person who originally requested Child benefit 17 years ago I am now culpable for the full payments of the 23/24 year as I earned over the threshold. I have spoke to both both departs child benefit and self assessment and to say they where not much help was an understatement. I earned 84k last year, and paid just over 20k in tax and paye. what should I be putting on my self assessment, should it just be the full yearly p60 amount, or do I deduct tax, paye, and pension contributions which show in my gross pay before deductions. To say I feel sick is an understatement, I am estranged from my ex and have no contact so its not even if we can share this, I pay for everything for my kids which we split 50/50. Assuming I have to pay back the full amount £2900 what does a payment plan look like as this will cripple me money wise even if spread over a year.

Hi,
We cannot view your personal records on the forum. Please contact our team for advice on your query:
Self Assessment: general enquiries
Thank you.

I have contacted them, they knew as much as me.

Is there no appeal procedure for this? I have not received a penny of the payments but will have to pay the fine.

Hi,
Sorry, we cannot advise about individual cases on this forum.
For guidance please contact the Child Benefit Office:
Child Benefit: general enquiries
Guidance about contesting a tax decision is available at:
Disagree with a tax decision or penalty
Thank you

I have as stated they where of no assistance. My query was more to the general public who seem to know more than hrmc. Your call centre has been down all afternoon but I will call tomorrow again and wait an hour for someone to answer.