How do I unlock if I have the codes?

[OldB4]

I have a ZTE MF683 that I have the unlock codes for already and I wish to enter them but I cannot find anywhere on the web that states how to unlock the device once you receive the codes. The carrier does not pop up an error message when I put a competing SIM chip in this USB modem like it does in a conventional cell phone, so I am not sure how to supply the unlock code to this USB modem device to unlock it.

All searches online seem to lead to DC-unlocker as the only way to unlock and I don't know if it is just captive marketing that has been set up or not or why there seems only one method described online. I see nothing else from the manufacturer to enter your unlock codes and I even phoned ZTE and they told me they didn't have anything - to check with the carrier. Every time try to use DC-unlocker it asks for an ID and password and outside of the fact when I look at the list of modems that it will unlock, the MF683 is in the list and the list says that unlocking is free.

When I try to sign in for an account, there is no option to select "the unlocking is advertised as free". There is only an option to buy credits. Why do I need credits if it is free? Thank you in advance.

What am I missing?

[Vincentas]

Use dc-unlocker and your modem will be unlocked automatically without entering unlock code.

Free unlimited is only if you have dc-unlocker dongle – a hardware key to dc-unlocker software. If you do not have this key, then you need top buy credits. You checked the price list that is for dc-unlocker dongle users. There is other list for other users. You can find list here: http://www.dc-unlocker.com/buy/user_prices

Username and password to use dc-unlocker software you will receive after buy credits. Credits you can buy here: https://www.dc-unlocker.com/buy