Determining the mobile service provider by the initial digits . . .

Different providers have different phone prefixes (some providers share the same prefixes with their sister companies):

• Extelcom: 973, 974
• Globe Telecom: 905, 906, 915, 916, 917, 926, 927, 935, 936, 937, 996, 997
• Next Mobile (Nextel): 979
• Smart Communications: 910, 912, 918, 919, 920, 921, 928, 929
• Sun Cellular: 922, 923, 932, 933, 942, 943