I am in the same situation. My study permit expires this Friday and I have nothing yet. I too have called CIC 3 times. on my second call, the representative sent an email to the visa office saying that my case was outside of normal processing times. The third time I called the rep said that they have to give the visa office at least 20 (work) days to respond to their emails. This means that even if I call the call centre, they cannot do anything until the four weeks have passed! So now I am trying to resign myself to waiting. I fully expect to go to implied status and make many more phone calls before the extension is approved. What else can we do? There is a very clear power relationship in with CIC.
However, its nice we have a forum to at least know that we are not alone