Civil service pension scheme owes me £21,300, five months after retiring

Scheme has not replied to complaints and Pensions Ombudsman says it needs evidence of that

I retired from the civil service five months ago and I’ve still not received my pension. I’ve complained to the Civil Service Pension Scheme (MyCSP) repeatedly, but it doesn’t reply.

The Pensions Ombudsman says they need evidence that MyCSP has not responded to my complaint. How can I provide evidence of a failure to reply?