SINGAPORE — For about seven hours yesterday, some frustrated StarHub customers were left grappling with intermittent voice call problems — with some also experiencing mobile data issues — as the telco scrambled to rectify the problem.

The interruptions to mobile voice services started as early as 9.30am, prompting disgruntled users to post on the telco’s Facebook page. Complaints ranged from being unable to receive or make phone calls, to problems with accessing their mobile data.

Some ComfortDelGro taxi drivers were also affected as StarHub also provides 3G data service to support the fleet — the largest in Singapore.

Ms Tammy Tan, group corporate communications officer for ComfortDelGro Corporation, said mobile data terminals, which despatch booking jobs to drivers in about half its taxi fleet, also experienced problems due to StarHub’s mobile service outage.

“The service disruptions, which started at about 11am, have also affected StarHub mobile users trying to book a taxi via our app,” she added.

In a statement last night, StarHub said it was still investigating the root cause of the incident. Earlier in the day, it had maintained that only voice call services were affected and SMS and mobile data services were working. However, after investigations, it reported that 3G data services were temporarily unavailable to some customers from 2.30pm and were fully restored by 5.30pm. These intermittent issues partially affected Comfort’s fleet of taxis as well, StarHub said.

Issues with its 2G and 3G mobile voice services in affected areas were resolved by 4.30pm. The telco had earlier said the disruption affected customers in only the eastern and western parts of Singapore, but it later said that based on updated information, the disruption was not limited to these areas. It did not reveal the number of affected customers.

The latest incident comes following a similar incident in June, where some StarHub customers were unable to make outgoing voice calls for hours due to a problem with its 3G services.

StarHub customers TODAY spoke to said they were unable to send or receive SMS messages. Ms Joey Tan, a housewife who lives in Telok Blangah, said she could not receive any calls or messages and had to rely on her home’s Wi-Fi network to access the Internet.

The long service disruption also affected business for transport company Mileage Enterprises, which operates excursion buses. The owner, who declined to reveal her name, said she was unable to contact her drivers or customers. “Wherever I (went), it shows there’s no signal. I can’t even get any business at all,” said the 37-year-old.

In a post on its Facebook page at 4.31pm, the Infocomm Development Authority of Singapore said it had been alerted by StarHub as to the connection issues affecting its mobile network and was investigating the matter.

In February, M1 customers suffered a six-hour disruption to call services. M1 also holds the longest disruption for a mobile service operator so far for its 71-hour service outage in January last year, for which it was fined S$1.5 million. In 2011, a SingTel outage lasted 22 hours.