MTN said it will challenge the $3.9 billion fine imposed by the Nigerian Communications Commission (NCC).

The fine, which originally stood at $5.2 billion, relates to the company’s failure to disconnect unregistered SIM cards from its network in the country, as NCC stepped up efforts to verify subscribers amid terrorism concerns.

Following talks between the operator and the country’s regulator, NCC said it was prepared to reduce the fine by 25 per cent, with payment due on 31 December 2015.

The saga has however now taken yet another turn, with MTN announcing it has “instructed its lawyers to proceed with an action in the federal high court in Lagos seeking appropriate reliefs”, following a company review of the situation.

MTN said it is acting on legal advice that resolved “the manner of the imposition of the fine and the quantum thereof is not in accordance with the NCC’s powers”, and there are valid grounds upon which to challenge.

MTN is also advised that “in the current circumstances, in line with pending leading action, the parties are enjoined to restrain from taking further action until the matter is fully determined”, as is consistent with judicial decisions in Nigeria.

It added that it will continue to engage with the NCC to “try and ensure an amicable resolution in the best interests of the company, its stakeholders and Nigerian authorities”.

The situation has already seen the resignation of three senior executives, including its CEO Sifiso Dabengwa, in the wake of the fine.

Phuthuma Nkhelo, Dabengwa’s replacement, has been leading negotiations with NCC so far.