Check your connections. bad connections can make a battery not charge or not power the phone.
First clean battery connections, if this does not correct problem the battery needs replacing.
Are your battery cable connections clean and tight ?
Go clean the battery connections, recharge the battery and then start. The connections you have now are just enough to turn on lights but not good enough to draw the power needed to turn the engine over. Clean the terminals and connectors and make sure they are tight. If after you clean the terminal connections it stil won't crank, then you probably have a dead cell in yoru battery but try the connections first before you go buy another battery.
This could be the voltage regulator. Both the positive from the battery and the starter would be connected to it.
Use baking soda and cotton swabs. If really bad you may use sand paper to clean connections.
Check your cables for corrosion; if there is any,clean them or replace them. Clean the connections at the starter and clean all grounding wires; test the starter regardless if you think it is good. Clean the battery terminals.
Corroded battery cables. Remove the battery cables, negative first, and clean the cable connections and the battery posts. If that does not help the battery needs charging or is defective.
Double check the battery connections, be sure they are clean and tight. Be sure the battery is in good condition and fully charged (12.68 V). Be sure the connections at the starter are clean and tight. Be sure the negative battery cable connection at the engine is clean and tight. Be sure the vehicle is in park or neutral. If all this checks out okay, the starter may be at fault.
You have a voltage drop in either the positive or negative battery cable. Clean all of your cable end connections ( at the starter, the engine block and again at the battery terminals). You have a voltage drop in either the positive or negative battery cable. Clean all of your cable end connections ( at the starter, the engine block and again at the battery terminals).
Its bad Clean the battery connections and make sure the connections are good. If the battery has been tested, has it been tested under an actual load, not just by placing the meter on it? also if the cells of the battery are beginning to break down, it will discharge at inopportune times,
Double check the connections at the battery. Be sure and clean the connections with a stiff wire brush and apply a light coat of grease when you reconnect the battery posts. --Modified If that doesn't work you need to check your ignition switch!!!