He noted that 7-Eleven Malaysia Holdings Bhd had done so after mistakenly charging the 6% on newspapers.
"Customs GST director Datuk Subromaniam Tholasy is currently meeting the telcos to discuss the matter. Such big companies should not be making such mistakes," he told reporters at Parliament House.
To a suggestion to set up complaint counters at shopping malls on the GST, he said he would bring up the matter to the Customs Department and Domestic Trade, Co-operatives and Consumerism Ministry.
Ahmad warned the telcos that they could be hauled to court if they insisted on imposing the 6% for prepaid top-up cards.
He revealed that a total of 815 complaints were received by the Customs Department on Wednesday - the first day of the GST’s implementation - and 40% involved top-up cards.
He added that the GST implementation had taken off to a good start as the Government had expected thousands of complaints but only received 815.