The suit, led by Celia Sankar of Elliot Lake, Ont., is seeking compensation for more than a million people in Ontario. It alleges Bell breached its contracts with those customers by expiring remaining credit balances too early or for imposing expiry dates at all.
Sankar launched the suit in 2012 after the balance on her prepaid plan was "seized" by Bell twice in three years.
The plaintiffs argue prepaid plans are like gift cards and are thus subject to Ontario's Consumer Protection Act, which says gift cards cannot have an expiry date.
Those affected were customers with Bell, Virgin Mobile Canada or Solo Mobile who had balances remaining in their accounts expire between May 4, 2010 and December 16, 2013.
The plaintiffs are seeking $100 million in damages.