Will my cell phone still work...?

I know I already asked this question, but I didn't get any answers to it. So...yeah. Anyway, I am going back to school shopping soon, and my parents said I would have to pay for my own cell phone. I'm fine with that, it's just that I don't really want to spend money on a phone with my back to school money. I have a phone that I got for Christmas 2011. It's a black LG cell phone. It's nothing fancy. Just a flip phone. I lost the charger to it a couple of weeks in. I know...we in the midst of a move, but yeah. I lost it. I don't mind paying for another charger. But I told my mom I wanted to see if I could use my old cell phone, and she said I couldn't. She said that if you don't add time on it for a while, it won't work. I mean, you can't call or text anyone. I was just wondering if this is true or not. I really want to be able to use this phone and just wait until I have enough money saved up where I can get a nicer phone. But I just need to know if using the LG cell phone is out of the plan. I just really need to know if after I charge it, I can still add time to it and call and text normally. Thanks!