SingTel's 4G mobile users will end up paying twice as much for their excess data charges from next month. The telco had earlier quashed rumours of this change in its charging.

From Sept 16, any usage in excess of a customer's data allowance - which starts from 2GB - will be billed $10.70 per GB, capped at $188 per month. The new rates are double the current promotional rates of $5.35 per GB, capped at $94 per month.

SingTel in letters and text messages to its customers said that the promotional rates were supposed to have ended in January but it had extended the promotion for another nine months.

Affected customers are those on its fourth-generation (4G) mobile data plans, all of which are bundled with tiered mobile data charges. As of June 30, the telco had 537,000 4G customers. Customers contracted on its 3G plans will not be affected unless they renew their contracts after Sep 16. If they renew before Sept 16, they will still enjoy the old rate of $5.35 per GB of excess data.

Similarly, those on its Broadband on Mobile plans - which allow laptop users to go online wirelessly via a 3G SIM card encased in a plastic dongle - will also not be affected unless they renew their contracts.

The telco had in June quashed rumours about the imminent increase after a flurry of complaints from netizens.

Fury erupted when a user of the HardwareZone website posted a screen capture of the telco's "frequently answered questions" webpage showing the new rates, which would take effect from July.

SingTel responded with an apology and said the information was "erroneously posted" on its website It also said it would notify customers in advance should there be price changes.