Hi sksksk,
It can take up to 8 weeks for your payment of voluntary contributions to be reflected on your Personal Tax Account (PTA).
If you could keep checking your PTA to ensure that it has been allocated as you wished.
If your payment is not recorded after the 8 weeks then please call our National Insurance Helpline on 0300 200 3500 (from the UK) or +44 191 203 7010 (from overseas) and they will be able to help you further.
Please have your payment details handy if you do call the National Insurance Helpline.
National Insurance: general enquiries
Thank you.