Note: before proceeding with steps below, insert operators sim card that does not work with device. For example if it's locked to operator "A" insert operator's "B" sim
Launch DC-Unlocker client software
Select manufacturer: ZTE modems, model leave Auto detect (recommended)
Press "Detect" button (Big magnifying glass)
Wait till DC-Unlocker fully detects device
Open Server tab, enter your username and password that you received after credits purchase. Click "Check login". (you can buy credits here www.dc-unlocker.com/buy).
If DC-Unlocker/Vygis/Rocker/Infinity dongle is connected, do not enter username and password, only click "Check login"
Open Unlocking tab, click “Unlock”
Wait till you see a message that modem is unlocked
After you see that modem successfully unlocked, restart it by disconnecting and connecting back. You might need to disable Diagnostics port for device to function again. For this detect it once more on DC-unlocker, then in unlocking tab press " Disable diagnostics port" and reconnect modem. Now you can use it with any SIM card.