Who is meant by Qazi Shahr and who elected him? What types of call or instruction do you mean? These matters are not clear in the question. To know the characteristics and conditions of Shahr Qazi and their selection mode, study the book ‘Al-Heelah al-Najizah’ written by Hadhrat Maulana Ashraf Ali Thanvi (رحمة الله عليه).
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband