Who do I inquire about my Social Security Disability payments being reduced?

I started receiving Social Security Disability back in May, and at first it was a relief. But $765 per month is not enough to live on. My other services were reduced to nothing helpful once I started receiving this paltry amount. I now go without meds, including blood sugar, blood pressure, heart, and others because I cannot afford them now,

Anyhow, I’ve recently found that my 765 per month is now only 740— I haven’t a clue why the reduction. I do get medicare parts A and B but am gouged with 150–200 dollar bills for regular medical expenses anyway, such as Labcorp and Semms Murphey for routine procedures.

I need every dollar of my disability money just to eat and minimally medicate myself. Who should I call? What can be done about this?.