As far as I have read in local newspapers VoIP calls are allowed for personal use.Any commercial activity like selling VoIP calling cards or calling through internet cafes for monetory gains are not allowed.You may buy VoIP calling card on line only for self use.Selling VoIP cards locally is not allowed since the sellers are not commercially registered to carry out these activities and their trade and income cannot be monitored ,moreover income from such activities may be used for illegal purposes.
Local telecomms are also loosing out their lions share of income from VoIP is also one of the reason.