Robert Nicol

Hi, I worked overseas in Australia from 2011 to 2018 and consequently had an underpayment of 1 year short of full NI contributions. I made a voluntary payment by cheque on 13 April 2023, and the cheque was cashed according to my bank account records on 16 May 2023. I paid by cheque following HMRC/DWP advice, including my name, NI number and year I wished to pay for on the back of the cheque and covering letter included with the cheque. I was unable to get a response from the call centre at that time, and after trying again multiple times today I am still unable to speak with someone regarding this matter. How can my record be updated after all this time, so that the payment taken is credited to my NI account?