MTN Group Ltd. said it is engaging with Nigerian authorities after the country’s telecommunications regulator imposed a record $5.2 billion fine on Africa’s largest phone company for failing to disconnect unregistered sim cards.

Chief Executive Officer Sifiso Dabengwa “is engaging with the Nigerian authorities on the regulatory aspects of this matter,” the Johannesburg-based company said in a statement on Friday. Senior management and the company’s advisers are in contact with JSE Ltd., which runs South Africa’s stock exchange about the timing of MTN’s Oct. 26 notice to the bourse about the fine, it said.

The Nigerian Communications Commission said late on Thursday that MTN has until Nov. 16 to pay the fine. Nigeria is MTN’s biggest market with 62 million customers as of September. The telecommunications industry contributes about 10 percent of Nigeria’s gross domestic product and MTN is the nation’s largest mobile operator with 42 percent market share.

MTN dropped 0.3 percent to 154 rand by 9:04 a.m. in Johannesburg, declining for a fifth day.

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