How can I resolve back pay issues regarding meal deductions?

Back in June of 2017 I got married. November of 2017 I submitted a 4187 to stop meal deductions and it never went though. Come January of 2018 I submitted another 4187 to start meal deduction due to it was required for a school I was going to for a month. I was still getting meal deductions at that point. In February of 2018 I pcs'd to fort carson Colorado. I submitted another 4187 to stop meal deductions shortly after being there and it didn't take effect until April 2018. When I addressed my back pay issues with the post finance office they only gave me back pay for the month of march. Reason being according to them the post is only liable for the back pay from the date I signed into fort carson Colorado. In order for me to get the other 3 months of back pay (Nov17-Feb18) I have to present the original 4187 I submitted at my previous duty station back in November. I contacted my previous duty station's S1 and they don't have it on record. All of my LES's clearly displayed I was still being deducted for meals from November of 2017 to March of 2018. Any advice on resolving this situation would be appreciated.