Can you resubmit a claim after getting the check for it?

We recently had a therapist who input a lower amount of total units for care, so when the insurance company got the claim it was only for 1/4th of the services. She did not catch the problem until we received a check in the mail for a much lower payment than expected. We tried to re-submit those claims after updating them, but they were denied (not rejected). I am thinking this means that we have to accept the lesser payment since those claims had checks sent out; but wanted to confirm. Thanks for the info!