By Diane Bartz WASHINGTON (Reuters) – U.S. mobile phone users have likely paid hundreds of millions of dollars in unauthorized charges crammed onto their bills, according to a report released by the U.S. Senate Commerce Committee on Wednesday ahead of a hearing on the subject. Some carrier policies allowed vendors to continue billing consumers even when the vendors had several months of consecutively high consumer refund rates – and documents obtained by the committee indicate this practice occurred despite vendor refund rates that at times topped 50 percent of monthly revenues, the report found. In early July, a federal court in California shut down six companies accused of cramming more than $100 million in unauthorized charges on consumers cellphone bills, according to the Federal Trade Commission. It is asking the company to refund the unauthorized charges.