When a phone is unlocked, it means it can be used by other carriers.
To unlock your phone (with the exception of Samsung), it must be paid off, cannot be reported lost or stolen, and your previous account must be in good standing. you must pay off your phone, it cannot be reported as lost or stolen and your account must be in good standing.
For Samsung phones, make sure that the phone was not purchased from or for a specific carrier other than Altice Mobile. Usually, this means it was purchased at a company like Best Buy or Amazon or directly from Samsung.
Below is some specific information about the major providers locking policy:
Verizon: Until very recently, Verizon did not lock phones. If your phone is paid off with Verizon, you are free to take it with you. However, moving forward, Verizon will lock phones at the time of purchase until they have been in service for 60 days and are paid off.
AT&T: After 60 days, if your phone is paid off, you can request to unlock it. AT&T will direct you to a website and text you a code to enter to submit your unlock request. Please note it can take up to two business days to unlock.
T-Mobile: After 40 days, if your phone is paid off, you can request to unlock it by contacting customer service. They will send you a link and code to unlock your phone. Please note it can take up to 72 hours to unlock.
Sprint: After 50 days, if your phone is paid off and your account was established after 2015, it can be unlocked by contacting customer service. Please note it can take up to two business days to unlock.