Most Sprint and Verizon phones aren't SIM-locked. But the V20 can only work on Sprint or Verizon, and Verizon won't allow a Sprint phone on their network, so it's effectively "locked" to Sprint. (The technology that Spring and Verizon uses is different from the technology other carriers use, so the phones won't work on AT&T, T-Mobile or their MVNOs [like Straight Talk].)