Final NI Class 3 payment for 2022-3 not showing on record

I paid my final class 3 voluntary NI contribution payment over 12 weeks ago and it is still not showing on my record. Every attempt at phoning several phone numbers is unsuccessful and I am cut off. I get my pension in December 2023. I have 27 years of contributions but only 26 years are showing on my record. I worked in Spain and France for 18 years between 1986 and 2004. I did not know at that time that I could pay voluntary class 2 contributions to top up my state pension in the UK. Is there any way I can pay for these years now to make up my 35 years?

Hi DebClaire13,

I am sorry that you have been unable to speak to an advisor on our helpline, our lines are extremely busy at present. 
It usually takes up to 8 weeks to allocate your payment, however in some cases this can be longer.
Without checking your National Insurance records, I am unable to confirm if we have received your payment.
Please keep checking your Personal Tax Account for the tax year to show as paid.
Alternatively, you can try calling our helpline when lines are less busy. Or you can write to HMRC and request a receipt for your payment.
The address to write to is shown below.
National Insurance Contributions & Employer Office address
PT Operations North East England
HM Revenue and Customs
BX9 1AN
Unfortunately, it is too late to pay for any years prior to 2006-2007.

Thank you