khoi_k_khoi_k, Sorry to say I don't agree with you too. VOIP itself is not illigal. It's new technology and New technology survives due to its efficiency.  It's NTA who didn't allowed to use VOIP NOT because of incompetitive, IT's because of their MONOPOLY. If it is due to incompetitive, there are big companies who indeed pay tax and want to establish VOIP connection. But NTA don't allow to do these coz NTA don't want to give any big deals except NTC.
NTXT, if you don't believe UTL did those illigal activities, You or UTL can file case against me and then I can produce sufficient proof for that. I got proof for all these activities.
Next, I agree with you that these days other people are doing these kind of activities using different SIM cards. What do you say about it, are those people are using VOIP coz VOIP is incompetitive technology??
IT's completely due to monopoly of NTA and NTC.