Google Adwords has for a while now incorporated call forwarding into their conversion tracking. This has only recently become available in Australia so chances are, if you are using Adwords and calls are important, then you should be tracking these as conversions.
For a little bit of info on how to do this you can check out some instructions here. However if you have already started using it, then Jimmy automatically pulls call data into conversion reports.
Conversion granularity will be coming soon so check back soon for this cool new feature.