If they want to get together and form a group dedicated to the principle of "give us more money", that's cool (to the extent that Indian antitrust law allows it) and I have no objections. But they won't get much media traction that way.

What they're doing instead is telling the media they've been cheated - that they deserve more money, and Zomato's acting unethically by giving them the advertised service for the agreed price. I'm not sure that's an honest way to look at the situation.