super High Cell phone bill! Having Guilt depression!?

[Peace]

Somehow I managed to turn a $35 cell phone bill into a $264 one! I am 17 and I feel terrible and depressed because my mom pays it and she is having money problems. Sadly this is not the first time 2 times before it was $99 and $63 another month. Its just I feel like I have no right to be happy with my mom suffering with the bill because of me I really didn't mean it to I didn't notice it. As soon as I found out I had to call her and tell and she told me a lot of things like how I could do this to her and that she trusted me which made me feel worse. I just cried myself to sleep. It sounds real dumb to cry over it, but my moms my best friend and I feel like the worlds worst daughter. What can I do??? PS: I have no money to help out