MTN has made a payment of 30 billion Naira ($98 million) to the Nigerian government in part settlement of a 330 billion naira fine imposed on the telecoms group for not disconnecting unregistered SIM cards.

According to Reuters reports, an MTN source revealed on Thursday that the Africa’s largest telecoms company has already paid 80 billion naira of the total amount owed.

The fine is due for payment in six installments over three years. MTN Nigeria was originally fined $5.2 billion last October for failing to deactivate more than five million unregistered SIM cards, but the fine was reduced in a settlement that paved the way for MTN to list its subsidiary on the Nigerian Stock Exchange.

Nigeria has been cracking down on unregistered SIM cards, concerned that they are used for criminal activity in a country fighting an insurgency by Islamist militant group Boko Haram.

MTN, which operates in 20 countries, had set aside $600 million last year to pay the fine. ($1 = 305.45 naira).