The Nigerian Communications Commission (NCC) has agreed to reduce MTN's (MTN) fine to $3.4bn, payable no later than 31 December 2015.
MTN said on Thursday it had received the formal letter from the commission on 2 December and was "carefully considering" a reply.
"The executive chairman Phuthuma Nhleko will immediately and urgently re-engage with the Nigerian authorities before responding formally, as it is essential for the company to follow due process to ensure the best outcome... all factors having a bearing on the situation will be thoroughly and carefully considered before the company arrives at a final decision," the company said.
MTN Nigeria had originally been fined $5.2bn by the commission for failing to deactivate 5.1-million unregistered SIM cards on its network.
Nigeria is MTN's biggest market with 62-million customers, followed by SA.
Source: BDpro