The thing is, they weren't small phones. People didn't smuggle them in their colons - they used code systems to arrange for their friends to throw things over the fences in particular places. Mini-riots were organised to coincide with throwovers. Drugs get in the same way.
There were a whole lot of more inventive methods used too. Suffice it to say that the problem is not the size of phones. It's that if you deprive people of their freedom, they spend all their time thinking about how to get it back. They will eventually work out how to get a little piece. Tiny phones won't make the blindest bit of difference.