All three telcos have decided not to charge customers on contracts for their 4G add-on services after the industry regulator stepped in to investigate the matter.

It came after StarHub announced plans last Tuesday to start charging for the 4G add-on, which it currently offers for free - as do SingTel and M1. It plans to charge most of its 4G customers $2.14 a month from June 1 for the add-on service.

An online poll of almost 1,000 people by The Straits Times last Friday revealed that close to 90 per cent of all mobile users thought that they had already bought a 4G mobile plan and did not know 4G service was merely an extra with a 3G plan.

In a statement Wednesday evening, the Infocomm Development Authority (IDA) said "there is significant consumer confusion over the service plans they signed up for".

The IDA also noted that the mobile operators "could have done more at points-of-sale and customer interface channels" to communicate their 4G position to subscribers. "Telecom operators should not change prices mid-way that affect customers with minimum term contracts, if they were not clear to customers upfront what those price changes might be."

Few other countries operate such a system. The free add-on is valid for a limited period, after which the usual price of $10.70 a month may kick in.

In a letter to The Straits Times forum published on Tuesday, reader Albert Wong Kwan Wei questioned how all three telcos arrive at $10.70, suggesting that a fourth telco be allowed to operate here to keep prices competitive. "Our population has increased over the years, and it may be time to open the market to more competitors," he wrote.