Mobile phone operator Idea Cellular reported a better-than-expected 30 per cent rise in quarterly profit, continuing to win market share through strong subscriber additions, which sent shares surging nearly 10 per cent. Himanshu Kapania, MD of the telecom company says growth in Q4 has been on account of a rise in voice subscribers, which will continue to grow. He adds that voice rate remains a challenge, but non-voice rate has improved.