I know you have already accepted an answer, but it seems that there is one key issue that you missed: You should be nice in teaching but uncompromising about cheating.
There should be a clear statement of the rules on your exam. Whether or not the rules are stated somewhere in the university rules, you should state them explicitly on the front page, something like:
During the exam, you are not allowed to talk or communicate via any means.
If you need to speak to the examiner, stay in your seat and raise your hand to alert the examiner.
If you break any of the rules, or attempt to cause any disruption, you will be given a zero.
Make sure they are told to read the rules in the few minutes before the exam itself. And then you have to be prepared to actually enforce the rules! This means that it would be a good idea to have a small test halfway through the semester where you do exactly the same, to prepare the students for a firm stance on rules. At least, even if they get a zero for the small test it would not affect their grade too severely (because we're kind of course).
Why do I emphasize this? It is because it allows you to effectively and cleanly deal with disrupting an exam, simply because it is covered clearly under the rules, and the students have simply no excuse.
