Has anyone been successful correcting Survivor Benefit Plans after retirement and was money refunded?

My husband and I elected to decline the survivor benefit. Unfortunately the dates were not signed correctly and it is now being taken out of his retirement pay. He was not afforded the option to review his paperwork in person prior to retirement because of COVID, so the error was not caught. We are now being told the only option is to wait 24 months. We have submitted a record chance request, but are told this will take approximately 18 months. I have no idea why the rules are so strict when it is clear we declined the SBP with the notarized signature.