Empirical evidence on merchant calls

I wonder if there is a way to collect empirical data on the number of times a merchant is called in a day. For example, for Plumber John, can we find out how many calls have been made to him?

Now, I know that it is almost impossible to get this data out of a regular phone company, but what about the VoIP providers, like Vonage? Perhaps they would be more amenable to providing aggregate data. Vonage is doing so bad financially they would do anything for a few dollars.