Who do I contact to address having been grossly underpaid with proof.

From January to September 2019, I received only $276.84 per month instead of the awarded $617.73, resulting in a cumulative underpayment of $3,067.01.
In 2020, I should have received $1,131.68 per month but only received $281.27. The cumulative underpayment for the entire year 2020 is $10,205.29.
In 2021, I should have received $1,251.29 per month, but there were discrepancies. received $635.77 for ten months and $992.04 for the remaining two months. .
Starting from December 2021 to March 2022, I should have received $1,325.03 per month, but I received $1,054.44. From April to September 2022, I should have received $3,517.84 per month but received $1,659.90.
From October 2022 to July 2023, I should have received $3,823.89 per month, but received $1,926.34.

This is just scratching the surface of this situation who should I contact every time I ask for an audit they give me the run around and say that it was never put in?