Unfair settlement

My cousin was working for medipost from April 2021 and in 2022 he started studying with the medipost training academy for a year in March 2023 he finished his course and due to company policy after studying one has to work for the company for a year before you can move to another company which he did but unfortunately he was dismissed in April 2024 he served the year that was needed after studying but when he got dismissed he was not paid his salary as he was told that the money went to the company as his year of service was not complete but it was their admins fault as they captured wrong information as he has a certificate showing when he finished his course in March 2023 and March 2024 he 1year of service was served till this point the company has not paid his salary or made any means of communication as to how to resolve this matter..