LG Voyager VX-10000

not sure if this question has been brought up in previous forums but i must ask. just purchased the Voyager saturday and did not realize how it holds NO charge; therefore i must get a car charger b/c of my job. the charger sold by VZW is $25 with my corporate discount; i found an after market for $12.99. i've been told by VZW NOT to use after market chargers b/c it can damage the phone. is that true? wondering if anyone out there is using an after market car charger and if so, how is it working out for you & how long have you had it? wondering if VZW is just trying to make a sale. thanks.