Why cant I pick up any network

Hi My Galaxy S2 suddenly lost network I put sim in another phone and it works fine, I have not dropped phone and everything else works even wi fi, its only the network connection thats packed up, I have tried another network sim but thats the same it says emergency calls only . I have tried cleaning contacts with Iso Alcohol but no use all connections seem ok, I have even tried a factory reset but still nothing, and I have paid the bills Ha ,any ideas my friends please ? Kev