Question:

Is calling the adhan a  sunnah or a wajib?

Answer:

For the five daily congregational prayers and the Friday prayer it is a sunnah muaqqadah (emphasised Sunnah) which is very close to being wajib (compulsory).

And Allah ﷻ knows the best

Imam Ahmad Rida Khan رحمة الله تعالى عليه

Translation by Dr Musharraf Hussain Al-Azhari Translator of Majestic Quran, www.majesticquran.co.uk