What is the difference between U and U1?

[Kanarena]

I'm using S906U1 and CSC is XAG(SIM), XAA(device)

[Josephigloe]

U is carrier locked and u1 is carrier unlocked so you can take a u1 phone and connect to any carrier.

[BEN83]

U also can be carrier unlocked model of phone and that can be also used on any other carriers.

[usermzeJaY3BsM · Accepted solution]

The U means that the device is a US variant device.  if it has a 1 after it then it was factory unlocked.  A U device can also get unlocked, if you meet the carriers criteria (like fully paying off the device, and then requesting an unlock)  I.E. if it has U1 it is a device that was never carrier branded or locked whereas a U device MIGHT be unlocked, but was produced with Carrier Branding by whichever carrier it was initially produced for.

[sandypam]

My phone won't make calls Satsuma u1 nit responding