Telco StarHub's sub-brand Giga has apologised for a spate of service disruptions and billing errors that have affected some customers, several of whom appear to be new to the brand's contract-free mobile plans.
More than 70 users took to the brand's Facebook page last week to complain about having difficulties with their cell and Internet service, with many noting that they had been overcharged repeatedly by the company.
In response to queries from The Straits Times, Giga on Tuesday said that it had rectified the "temporary issue", which arose from an earlier scheduled maintenance that had inadvertently affected "a small number" of customers.
The company said affected customers had encountered "brief service difficulties" or unintended charges in their bills.
Ms Aletheia Y. P., the head of Giga, said the company "immediately started service recovery work for impacted customers, as well as provided them with regular updates".
"We confirm that the issue has been fully rectified and all unintended charges will be fully refunded within a week," she said.
However, affected customers ST spoke to said the response from the company has been slow.
Several of the affected customers who wrote on Giga's Facebook page said they had difficulties using their new phone plans last week.
Mr Terence Ong, 27, a student, said he tried multiple times to get a response from the company through its chatbot and on Facebook when he could not get any cell and Internet service after receiving his Giga SIM card on Jan 6.
However, the company's response was intermittent, once replying only after six hours and at other times not replying at all.
Giga was able to resolve the issue only on Monday evening, said Mr Ong, who had no cell service for five days.
He also said the company attempted to charge him $468 in a span of three days, although the plan he signed up for was supposed to cost only $9 in the first month.
Similarly, Giga user Augustine Jiang, 32, was billed multiple times by the company last week. The civil servant changed to a different Giga plan last week, but found that he was billed $256.32 in total over three days, despite signing up for a plan that should have cost $10 a month.
The company continued to add to the charges even after he e-mailed it about the error.
Said Mr Jiang: "It took them three days before they had an official message on their Facebook page acknowledging the problem.
"I was kind of worried in between, because their chatbot was very slow and inactive."
Giga said it is contacting affected customers to offer "a sincere apology" and a one-month free plan subscription.