SIM card that lasts a month In America?

I'm heading up to Dallas in about 2 weeks, and I need to call from my phone, I have a Lebanese Line. I thought about getting roaming on my phone but i heard it's expensive. So my aunt suggested getting a SIM card in Dallas. She said there is one that cost about 40$ and has unlimited texting and calling from T-Mobile. Also.. I Have a blackberry so I need to know if It will work for the blackberry. Thank you <3