Africa’s largest mobile operator MTN Group on Wednesday named its Ghana chief executive, Michael Ikpoki, to head up its key Nigerian business, in a job reshuffle sparked by the abrupt resignation of its chief financial officer.

Nigeria is the second-biggest revenue earner for Johannesburg-based MTN, which has operations in nearly two dozen countries in Africa and the Middle East.

Harvard-trained Ikpoki is replacing Brett Goschen, who took over as CFO after Nazir Patel resigned this week following an investigation into allegations against him.

The company has said the allegations against Patel were over governance and would not impact its financial results. It has not given any other details.

Serame Taukobong, chief marketing officer for MTN’s South Africa business, will take over as head of Ghana.

MTN’s shares have dropped 7 percent since the announcement of Patel’s departure after close of trade on Monday.