Unlocking a phone removes network restrictions on the device and allows you to use any networks sim card in it. This means that you can use any card from any country and take advantage of other networks deals. Once unlocked, it will be permanently unlocked. It will never need to be unlocked again.
If your device is on contract, we can usually still unlock it without an issue. Be aware this does not stop the device from becoming blacklisted if payments for the handset are not kept up to date or if the device is marked as lost or stolen. This is controlled by your devices IMEI number and cannot be altered. We have no control over your devices blacklist status, it is recommended to check your devices status using imei24.com or by purchasing a CheckMend report before buying a secondhand device. If your device is on a Corporate or Business plan, please mention this before booking with us as some devices and networks are not supported in this situation.
Please be aware that network unlocking your device DOES NOT remove it from a blacklist and DOES NOT remove iCloud locks.