The Indomitable Lions had initially refused to travel to Brazil for the tournament due to a disagreement over how much they would be paid.
"You have to be objective and realistic; [the bonus row] has played a role," M'Bia is quoted as saying in AS. "In a great worldwide tournament, certain rules must be respected and we paid for our mistakes. No one wanted to do so badly.
"Despite what you people think, we are very united. There are no conflicts, no problems. We are simply disappointed by not getting good results despite all of our work and the very good things in training.
"It's a matter of pride, as an African and as a Cameroonian. We must improve our image and not finish like we did in 2010 when we ended catastrophically, with zero points."
Cameroon are unable to qualify for the knockout stages of the tournament after losing their opening two Group A games.