Mint is now T-Mobile.
In fact, all cell-phone services are either T-Mobile or Verizon or ATT.
Maybe different processing centers, but same cell towers as the big three.
yup.
They all buy airtime from one or more of them. Typically you are stuck with one primary carrier.
roaming doesn’t happen. One of the reasons an account with the big 3 costs more is the roaming agreements. You won’t know what carrier your phone is actually using, but it might not be the one billing you in some areas.
In fact, all cell-phone services are either T-Mobile or Verizon or ATT.
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or Spectrum