SBI has classified a term loan account of Mahanagar Telephone Nigam Limited (MTNL) as a sub-standard non-performing asset (NPA) due to non-payment of instalments and interest since June 30. The total outstanding in the account is ₹325.5 crore, while the overdue amount is ₹281.6 crore. The bank has threatened MTNL with legal action in case of non-payment.