The ongoing fixed-mobile substitution (FMS) trend doesn't stem from all mobile users equally. We identify mobile users with very low mobile usage patterns, who represent about one-fourth of the mobile base, as well as a much smaller group of users who use their mobiles exclusively for all of their calls. The various groups display radically different spending and non-voice service usage patterns. Operators need to apply product strategy targeted specifically for each group to further stimulate mobile usage.