My son bought a nokia

Question

my son bought a nokia n95 of e bay worked for 2 days then said sim card regitration failed he has tried other sims but does the same,its unlocked for all networks he is upset as we cant get in touch with seller as he has vanished,plus he never paid through pay pal so they cant help,e bay have tried to help but as the seller has gone has he bought a expensive paper weight