The 32-year-old was one of nine players to lose his job when the Swiss side proposed reducing the wage bill of the first team as an emergency measure during the coronavirus pandemic.
The Swiss players’ union has indicated its support for the players, with Song intending to take legal action.
“My lawyer will take care of it, it’s gone to Fifa,” the former Cameroon international told French broadcaster RMC.
“We’re going to defend our right. We played a friendly on Friday and we were supposed to meet with the president on Monday, then Tuesday. We had no news.
“We received a WhatsApp message on Tuesday afternoon to tell us that everyone had to sign a paper saying that we’d reduce our salaries, that we’d be paid around €12,000.
“We had to return the paper by 12pm the next day. We received this document without an explanation.”
He added: “We decided together to not sign this document. We wanted to discuss it.
“I’ve not committed any professional mistake. Every club talks to their players to reach solutions.
“I don’t understand what’s happened. Nobody can understand it.”
Numerous clubs have reduced the wages of their players and coaching staff due to the financial impact of coronavirus, including some of Europe’s biggest teams.
Barcelona and Atletico Madrid in Spain and Bayern Munich and Borussia Dortmund in Germany are among those to have cut wages.
In some cases, such as Bayern and Dortmund’s, the cuts to players’ wages were voluntary.