SoftBank has said it may book a charge of as much as US$1.2 billion when reports earning next month. Including today's trading, SoftBank's market value has dropped by 1.92 trillion yen (S$23.6 billion) this year. Sprint's US$1.5 billion of 7 per cent bonds due 2020 plunged 8.25 US cents on the dollar to 60.75 US cents in New York, according to Trace, the bond-price reporting system of the Financial Industry Regulatory Authority. That's the lowest since issuance in August 2012. Moody's Investors Service lowered Sprint's credit rating in September to B3 from B1, or six levels below investment grade, citing "brutal competition" in the US wireless industry that will pressure even the strongest operators. The ratings firm also cast doubt on the wireless company's ability to refinance more than US$12 billion of debt coming due in the next five years without additional support from its majority shareholder - SoftBank Group. BLOOMBERG