The figure includes a $1.6bn cash payment and $800m of company debts, which will be written off.
T-Mobile, which is owned by Deutsche Telekom, said that the purchase will increase its share of the market in the Caribbean and the south eastern US.
The deal adds customers in North Carolina, South Carolina, Tennessee, the US Virgin Islands, Georgia and Puerto Rico, giving T-Mobile 15 million potential extra customers.
"The acquisition rounds out our domestic footprint, allowing us to service 98 of the top 100 markets and will significantly benefit our financial position by reducing roaming expenses," said an official T-Mobile statement.
AT&T, Verizon and Sprint currently rank as the top three US wireless service providers based on user numbers. T-Mobile is in fourth place with 27 million subscribers. The SunCom acquisition will add 1.1 million subscribers to that number.
The deal has already been agreed by Pardus Capital Management and Highland Capital Management, which own more than 50 per cent of SunCom's stock.
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