Don't know about others, but it seems you need to pay money to file antitrust complaints in India. From the link you mentioned:

What are the fees to be paid? [Regulation 49 of the Competition Commission of India (General) Regulations, 2009]

(1) Each information received under clause (a) of sub-section (1) of section 19 of the Act from any person shall be accompanied by proof of having paid the fee as under- (a) rupees 5,000 (five thousand) in case of individual or Hindu Undivided Family (HUF), or (b) rupees 10,000 (ten thousand) in case of Non-Government Organisation (NGO), or Consumer Association, or a Co-operative Society, or Trust, or (c) rupees 40,000 (forty thousand) in case of firm (including proprietorship, partnership or Limited Liability Partnership) or company (including one person company) having turnover in the preceding year upto rupees two crore, or (d) rupees 1,00,000 (one lac) in case of firm (including proprietorship, partnership or Limited Liability Partnership) or company (including one person company) having turnover in the preceding year exceeding rupees two crore and upto rupees 50 crore (e) rupees 5,00,000 (five lacs) in the cases not covered under clause (a) or (b) or (c) or (d).]