How to pay voluntary contributions?

I would like to pay for the following years, 2011/12 - £174.35, 2020/21 - £795.6 and 2021/22 - £800.8. When I try to do this online the only option it gives me which is close is 2020/21 - £795.6, 2021/22 - £800.8 and 2016/17 - £824.2, is there a reason why I cannot pay for 2011/12 as it's a smaller amount than for 2016/17? how do I go about paying for the years I want to pay? Thanks for your help.

Hi Graham03,
You will need to contact DWP, to confirm whether your State Pension will increase before you pay any shortfall for a specific tax year, to confirm doing so will increase your State Pension. Please call the Future Pension Centre to find out which tax year will count towards your State Pension.
The number to call is:
0800 731 0175 if you live in the UK
+44 191 218 3600 if you live outside the UK
You can also get a State Pension statement. To do this, go to GOV.UK and search ‘check your state pension forecast’.
DWP have an online form so that any customers who are unable to speak to DWP before the deadline can register their interest in paying voluntary NICS and request a call back.
 If you submit a request by the deadline (05/04/2025), you will be able to pay voluntary NICs after the deadline has passed at the rates that were applicable in the 2023 to 2024 tax year. DWP will contact you within 8 weeks to discuss the payment of voluntary NICs. Once DWP have contacted you and advised on the shortfalls to pay, you are given 31 days to make the payment. 
Once you have confirmed which tax years you need to pay for please use the following link for details on how to pay.
Pay voluntary Class 3 National Insurance: Overview - GOV.UK.
Thank you.