NI and Pension issue

I paid 1 year of missing NI contributions on 20 February 2023 via a direct bank transfer noting the ref no. given. I received a form to state why the payment was made and what for, which I posted back in June 2023. It is now September 2023 and this payment has still not been credited to my NI account. My state pension started earlier this year and is now being affected. Which department should I be contacting and can specific details be provided please?

Hi Ppps14,

If you could call our National Insurance Helpline on 0300 200 3500 they will be able to check to make sure that your payment has been received correctly and
for it to be allocated to your National Insurance account.

Thank you.