Rating agency CRISIL has downgraded its rating on the Rs 3,500 crore non-convertible debentures of Vodafone Idea Limited to 'B+' from 'BB' while continuing the rating on 'Rating Watch with Negative Implications'. The primary reason for downgrading the telco's rating is the lack of relief from the Centre after the Supreme Court (SC) on February 14 refused to grant relief in the Adjusted Gross Revenue (AGR) case, CRISIL said.