He is saying that he has dialled a certain phone number very often (or a lot of different numbers) with little success if any.

You can look up idioms like these on linguee: http://www.linguee.de/deutsch-englisch/search?source=auto&query;=die+Finger+wund So: sich die Finger wund + verb = to do s.th. till your fingers hurt/are sore/are bloody.

In this case it's clearly a hyperbola, and the intended meaning is as you say. But it is possible to work one's fingers sore, and it can be used literal.

Thanks. So does it mean that one will go to great length to get something done but not literally getty hurt?