Payments missassigned by agent - how do I rectify ?

Hi Firstly thanks for the great work the HMRC admins do here, it's a fantastic and comparatively quick service. Here is my issue: I helped my wife fill in a CF83, and we were informed that we could backpack 2020-2021, 2021-2022 ahx 2022-2023. She made three payments corresponding exactly to the amounts communicated in the letter for each of the three years. (The payments were made in GBP) Then these payments have been missassigned by the agent, with 2020-2021 only showing as full, 2021-2022 showing as partially full and 2022-2023 showing as totally empty. As soon as this happened we rang up and the lady who answered the phone acknowledged that she could see that a mistake had been made, but said she cannot fix it, and can only leave a note on the system. In the meantime my wife received a letter detailing the payment that needs to be made for 2023-2024. She made the payment. Now 2021-2022 shows as full, whilst 2022-2023 shows still as empty. Basically an error on top of an error. It's clear that the note has been ignored, and I need to speak to the person actually responsible for assigning the payment. I want to make further payments covering the time was at university (needs to be done before the 2025 deadline), but it would make sense to clear up these more recent payments first (she can't seem to use the new pay online functionality for some reason even though I did this successfully for my account). Can you advise what I should do?

Hi,
Sorry to hear of the problems that you’ve experienced with our service recently.  
If you could call our National Insurance Helpline again on 0300 200 3500 (from the UK) or +44 191 2037010 (from overseas), please ask for an
urgent referral to be made to our International Team for them to correct your payment of voluntary National Insurance contributions. 
Thank you.