A friend of mine told me that it was the practice of Bilal (R.A) to recite Salat and Salaam before Azan (call to prayer). Could you please tell me in the light of the Qur'an and Sunnah if this is a Bidah or a Sunnah?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

There is no evidence proves that the Prophet (Sallallahu Alaihi wa Sallam) ordered Bilal (Radiya Allahu Anhu) to invoke blessings upon him and send greetings to him before Azan or Iqamah.
Also there is no evidence that the Prophet (Sallallahu Alaihi wa Sallam) even sanctioned it. Yet, there is no proof that Bilal (Radiya Allahu Anhu) ever did it. Doing so is an innovation. The Prophet (Sallallahu Alaihi wa Sallam) said: "You must avoid novelties, for every novelty is an innovation, and every innovation is a deviation, and every deviation is in the Hell-fire". [Al-Tirmizi and others).
Allah knows best.