Airtel Africa has floated on the London stock market - and its shares fell as much as 15% in early trading.
The shares were priced at 80p but fell to 67p as trading started.
The company is part of India's Bharti Airtel.
Even so Raghunath Mandava, chief executive of Airtel Africa said: "We are delighted by the strong response we have received from the many high-quality investors from around the world.
"This is a proud moment for the team that has built Airtel Africa into the second largest mobile operator in Africa."