NEW DELHI: Telecom regulator Trai has received around six lakh comments on its consultation paper over 'Differential Pricing for Data Services' -- one of the important issues under net neutrality principles."Till Thursday, Trai received about 5,40,000 comments. These comments have suddenly come and mostly around Facebook 's Free Basics service. Today comments would have crossed six lakh," an official source told PTI.The last date for comments on the consultation paper is December 30 and for counter comments is January 7.Facebook has launched campaign where it is asking users to support Free Basics scheme under which the user can access some websites for free without paying internet charges.The regulator had received over 10 lakh comments on first consultation that it floated around net neutrality.A debate on net neutrality stirred across the country after Airtel decided to charge separately for internet-based calls but withdrew it later after people protested. Internet activists and experts flayed the operator for 'Airtel Zero' service along with Facebook's internet.org service.Amid debate over zero-rating plans and telecom firms offering discounted tariffs for accessing certain websites, Trai issued consultation paper seeking comments on whether such differential pricing should be allowed.