The advent of VOIP and VOIP numbers renders tracking almost impossible. A 'customer' can often choose the number he or she wants to use, with any country and area code desired. The only way to track it is to somehow find out which VOIP company holds access to those numbers. A little difficult. You would need absolute co-operation from several authorities - most probably outside your country. It would proably be easier to 'explain how a woman's mind works' as the joke goes.
EG For my two VOIP numbers I had a choice of a 'local' exchange number OR any UK exchange prefix.