How to convert this data in a format that cluto recognizes?

Hi, I am trying to analyze the datasets from a phone network. The data is in the format as follows:

A B
A C
D B
F G

where 'A B' implies A calls B. I need to find the networks of all the people who call each other.
How do I get this data in a format that cluto recognizes? The scripts available are conversion are for document data.

RE: You need to create a graph

You need to create a graph from the above data and provide that as input to the scluster program.
Read the sparse input format for scluster.