Adeola Odeku Street in an upmarket Lagos neighborhood boasts the highest concentration of bank branches in Nigeria — but when people need cash they turn to mobile money agents under patchy umbrellas clutching palm-sized point-of-sale devices, rather than the lenders.

"My business is to give you the money if you can’t get it there," Sani Abdulrahman said, pointing from his wheelchair to a branch of the United Bank for Africa — Nigeria’s third largest bank by market value — across the street, and its block of empty ATMs.

Abdulrahman is one of more than 2 million mobile agents operating across Nigeria — one for every 100 people — handling most of the country’s daily transactions and starving the formal banking system of cash. The Central Bank of Nigeria, looking to increase financial inclusion, encouraged their proliferation. But regulators now fear they are consuming the monetary system, undermining the fight against inflation and pushing the naira further from their control.