It would appear you ground operator may not have been using the correct callsign, or you would know his exact status. Offence under Art 91.
A/G operate in accordance with CAP 452 not CAP 413. AFIS operate in accordance with CAP 410.
Many A/G operators do not have the CA1308 signed by the radio station licensee who is responsible for ensuring they operate the station in accordance with CAP452.