A Solution to Waiting for Support Over the Phone

It seems that almost every month or so, I have to call tech support for one reason or another. And every time it happens, I take a phone, dial the number, put it on speakerphone and surf the web until somebody picks up. I can wait for hours sometimes, and then I just get transferred. So I came up with a solution.

Why can't they call us back? Why can't it be like this:

You dial the number. A computer picks up and tells you that all operators are busy, but if you could please enter your phone number as soon as one becomes available he will call you back. Thank you for your time.

This means no more waiting on hold for hours on end. I don't know how much it costs for a company to call you from Mumbai, but it seems like it would be cheap enough.