They probably endorsed it already to a support team who would be investigating your report and there is nothing much to do except to wait. Calling 211 would be the most convenient way rather than lining up just to make a follow up. You may ask 211 if your complaint was recorded.
I hope you have kept a receiving copy of your letter for reference in the future and a basis for your right not to pay the disputed amount pending on the results of the investigation. You do not have to pay the amount that is in dispute.