Shares of the Vodafone Idea slipped as much as 9 per cent intra-day on the National Stock Exchange, following Birla's comments and closed the day's trade nearly 6 per cent lower than the previous day's end at Rs 6.90. Aditya Birla Group's Idea Cellular had joined hands with rival telecommunications firm Vodafone last year to compete with the onslaught of cheap data and call being offered by rival Reliance Jio Infocomm.