Does the NI Contributions Office reply to letters?

I sent a letter Special Delivery to National Insurance Contributions Office, BX9 1AN, on 23rd July 2024 which was delivered the next day, 24th July. I am deaf and cannot hear the phone. I had to send a letter anyway as I included copies of invoices and other documents proving I was self-employed for tax years 2006-07 through to 2013-14. I want to make voluntary NI contributions for these years before the deadline of next April. The NI record on my Govt gateway account shows class 3 amounts but they should be class 2. Could you please confirm the letter has been received? My postcode ends with 5AP.

Hi
You can find out when you can expect to receive a reply form HMRC here:
Check when you can expect a reply from HMRC
Thank you