Because you aren't using the proper charger. Use the charger that came with the phone and it will take care of it. Verizon sent me a slow charger, which I use for overnight charging, but when I am still going to ouse the phone while on the charger, I use the charger that was supplied with the phone. Anytime I use the wrong charger, the phone SUCKS! Takes like 10 minutes to unlock the damn thing.