Ascension Health has signed a new contract worth up to $1.7 billion with a Chicago-based debt collection firm that was banned for Minnesota for alleged hardball tactics. The bill collector, Accretive Health Inc., said in a filing Wednesday with the Securities and Exchange Commission that it has a new five-year national contract. But neither Accretive nor Ascension will say how many of the system's 80 hospitals currently use the collector or will do so under the new deal.