Why can I not pay Class 2 contributions whilst abroad?

I completed the CF83 (once I found out about it) and subsequently received a letter confirming that I can pay reduced contributions whilst abroad. I left the UK in April 2003 and have been living in Africa for the past 20years. Prior to completing the CF83, I made payments, based on information on the State Pension web site, using the bank details for people residing overseas. Upon learning that I can make reduced payments, I wrote in asking for a refund of the difference between the standard Class 3 and the Class 2 that I was told I could pay. However, I have just received a letter saying that the previous letter was incorrect and that I "did not meet the conditions for payment of voluntary Class 2 contributions abroad" Can someone please tell me why, having been abroad for 20years, I have been precluded from paying reduced voluntary NI contributions.

Hi peter_r_c,
To be entitled to pay voluntary class 2 National Insurance contributions whilst overseas, an individual must be either employed or self-employed overseas and before they left the UK they were employed or self-employed.
To check why you are not able to pay the voluntary class 2 contributions you may wish to call our National Insurance Helpline on +44 191 2037010 and they will be able to check your National Insurance account.
Thank you. 
 

Thanks for your reply. Appreciated. I was employed for many years before leaving the UK, but not immediately before leaving ( took time out due to illness and spent a number of months in Africa, before finally moving there in 2003. And since leaving, I have been self-employed for every single year. I don't see the relevence or understand why, after having paid tax and NI in the UK for decades, I am not entitled to a refund of the difference between the full Class 3 payment I made from overseas and the much lower Class 2 which I was told I could pay whilst overseas.

Hi,
Thank you for your further contact.
Unfortunately, without looking at your records I am unable to comment on the reasons why you have been told that you are not eligible to pay at the Class 2 rate.
If you disagree with the decision, you can to write to HMRC at the following address:
National Insurance Contributions and Employer Office
PT Operations North East England
HM Revenue and Customs
BX9 1AN
Thank you.