That is ridiculous!
You could try using the opera mini browser on a prepaid local sim for browsing to your email online. You would need to enter the APN settings for this carrier onto your device to get it working but this is not quaranteed to work. I do not think instant Messaging will work via opera but you may be able to use the yahoo go application.
Look in the FAQ section for an article on running a BB on a generic data plan.
If your bb has wifi (I'm on the wap site & cant see) you could use that.