Online ordering service Grubhub is pushing back on a proposed nationwide class action spearheaded by a Philadelphia restaurant chain that claims the popular digital service is collecting undeserved commissions.

Last month, Tiffin Indian Cuisine restaurants filed a proposed class action lawsuit in the U.S. District Court for the Eastern District of Pennsylvania, contending that Grubhub was withholding millions from restaurants across the country because it charged commissions on “sham” phone calls that did not result in takeout orders. The online ordering company, however, shot back in court papers recently, saying Tiffin’s lawsuit failed to raise a claim.