Mobile phone users might have to spend more as the National Board of Revenue is expected to seek a hike in the supplementary duty (SD) on calls, data and other services in the coming fiscal year, said officials. At present, the users have to bear 15 percent VAT, 5 percent SD and 1 percent surcharge on their bill for phone calls, data and other usage. The rate of SD is likely to go up to 10 percent, said finance ministry officials.