Verizon, the country’s largest phone company, is buying prepaid phone seller Tracfone for up to $6.9 billion, expanding its low-income customer business.

Tracfone, a subsidiary of Mexico telecom giant America Movil, is a mobile reseller, the largest in the U.S. It doesn’t build its own network, instead paying companies like Verizon, AT&T and T-Mobile a fee to use theirs. Nearly two-thirds of Tracfone’s 21 million U.S. customers get their service from Verizon via Tracfone renting Verizon’s network.

“This transaction is aligned with what we do best: providing reliable wireless service alongside a best-in-class customer experience,” said Hans Vestberg, Chairman and CEO of Verizon. “We are excited about the opportunity to bring Tracfone and its brands into the Verizon family where we can put the full support of Verizon behind this business and provide exciting and compelling products into this attractive segment of the market. We are pursuing this important strategic acquisition from a position of strength given our very strong and prudent financial profile.”

Most U.S. cellphone customers are “postpaid” rather than prepaid — they pay a monthly phone bill. Prepaid customers are more likely to be low-income or have bad credit. Tracfone is a major provider of the U.S. Lifeline service, which discounts phone and internet service for low-income customers. Verizon said Monday that it would continue to offer Lifeline through Tracfone.

The deal consists of $3.1 billion in cash, $3.1 billion in stock and up to $650 million more in cash for America Movil based on the Tracfone business hitting certain performance targets after the sale.

Verizon said it expects the deal to close in the second half of 2021. Regulators must approve it.