Blackberry Bold 9700, on prepaid?

So, I used to have AT%26amp;T and the bill was crazy with my blackberry bold. I was wondering if I went out and brought a prepaid sim card if my blackberry would still run the same? I know there would be some differences, I would be getting a smartphone sim card as well, but AT%26amp;T said my phone wouldn't work the same, like the programs wouldn't work. I figured they said that because they were trying to get me to go back to the monthly paying of it. I wanted to know if anyone else has tried this, and what your opinion was on it. Please help. %26lt;3