Each betting firm is assigned a unique number, known as a pay-bill, which is used to process payments from users who place bets on their mobile phones and to pay off those who win.
Customers using basic feature phones rely on short codes assigned to each betting company.
Liti Wambua, the acting director of the regulator Betting Control and Licensing Board (BCLB), told Safaricom in a letter seen by Reuters on Thursday that licences for all 27 betting firms had not been renewed, pending the outcome of an ongoing inquiry about their suitability to operate in the country.
"Consequently, we request you to suspend their pay-bills and short codes until otherwise advised," Wambua said in the letter.
In a response, through its lawyers, Safaricom said it required time to carry out the order since abrupt implementation would result in shutting millions of users out of funds already deposited in the gaming wallets of the various betting firms.