Network unlocking
A network lock (SIM lock) is a software restriction set by a carrier and tied to the device's IMEI - often in exchange for a subsidised price. It's very different from a blacklisted IMEI (a phone reported stolen or unpaid), a status no unlock can lift since it isn't the same problem.
FAQ by brand
All devices
How do I know if my phone is locked to a carrier?
Insert a SIM card from another carrier: if the phone asks for a “network unlock code”, it's locked. With no such message and the network showing normally, the device is already unlocked.
What's the difference between a network unlock and a blacklisted IMEI?
A network unlock removes a software restriction set by the original carrier. A blacklisted IMEI means the device was reported stolen or with an unpaid balance to the carriers - a completely different problem that no unlock can legally solve.
After the unlock, my phone shows “not registered on network” with the new SIM?
Very often it's just a missing or wrong APN setting for the new carrier, not a failed unlock - something we check every time after an unlock.
Apple (iPhone)
Can an iPhone financed by a carrier be unlocked before it's paid off?
Generally not - the financing lock stays active until the carrier's conditions are met, whatever third-party unlock service is used.
Your problem isn't listed here?
Every device is different - ask for a free diagnosis or describe the problem directly on WhatsApp.