It has to be used on metroPCS since it uses CDMA for voice and text. For LTE, it'll use metroPCS LTE - and T-Mobile LTE where T-Mobile has allowed metroPCS customers to connect or where it has combined LTE networks.
metroPCS and T-Mobile 1700MHz LTE are the same band 4. It's also known as AWS. It uses 1700MHz for upload and 2100MHz for download. AT&T and Verizon also use that band.
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