I think there might have been a mistake when my school or college submitted my centre assessment grade for GCSEs

You can ask your school or college to check whether it made an administrative error when submitting your centre assessment grade or rank order information for GCSEs.

Administrative errors might include, for example, mixing up 2 students with similar names, or accidentally copying across the wrong data, but do not relate to the professional judgements of centres in giving centre assessment grades. If your school or college thinks it made a mistake, it can submit an appeal to
the exam board, but it must be supported by clear evidence that an error had been made.