A circular had been circulated making it illegal to sell activated SIMs or to have more than three SIMs with each operator, said Deputy Minister of Information and Communications Le Nam Thang.
The millions of pre-paid subscribers who had yet to register their personal information had three months to do so or they would have their services cut off.
Thang said the problem arose with service provider promotions in a nearly saturated market.
They were offering free credit with new SIMs, which people were using and then throwing away, he said.
Telecom operators were giving 5-6 per cent discounts to authorised agencies to sell mobile phone top-up cards but they were giving 26-29 per cent for new SIM activations, he said.
Not only were their promotions proving ineffective, because they increased operating costs and management difficulties, but they were adding to the number of “virtual” subscribers in circulation, he said.
A lot of SIM cards were having their future owners’ personal information falsified by agencies.
Thang said, however, he did not believe the new restrictions were strong enough and that other technical and financial measures were needed.
“If telecom operators keep running promotions it will be hard to control virtual subscriptions,” he said.
New mobile subscription in Viet Nam have skyrocketed from 19 million in 2006 to 25 million in 2007, to 74 million in 2008, to 98 million in 2009 and to 120 million this year.