Yay Ambiguity

My sister got her first cell phone for Christmas--a red Chocolate. Since my parent had never bought a texting plan for me, they decided to wait and see how much texting she did.

She spent $18.90 that first month. Mom and Dad sprung for the five-dollar unlimited plan.

Mom said, do you want to be on that plan, too?

I said (according to me) okay, that would be good.
I said (according to her) eh (my I'm-too-lazy-to-talk response).

Last month, I spent twenty bucks on texts. Oops.*

I am now on the unlimited plan.

________

*Needless to say, I wouldn't have spent this much if I hadn't thought I had unlimited texts. And I have sometimes texted for homework help.