It seems some of those routers are indeed SIM locked. Mine didn't work with a Telkom SIM when I tried it the first time.
However.
Using my l33t hax0r skillz I found a procedure to unlock it:
* Visit the hotspot page (usually my.hotspot) and append /hidden to the URL. Check the menu. There should be an option for SIM locking. You can try to disable it there.
* But you may also find nothing is that simple. Mine asked me for a security code in order to save changes. This is when you put on your hacker glasses.
* Try visiting the hotspot URL with /webpst appended - that gives you another hidden menu. Under the "service" section of the menu you will find USB options. Select the one with ADB included (usually the last one).
* When you plug in your router via USB it now shows a bunch of "Android device" entries. The chipset is Qualcomm, so those drivers should be the ones installing. If you can't auto install drivers, the one you are looking for is "QUALCOMM Composite ADB Interface-MI00".
* Then download ADB from Google (part of the Android platform tools - you don't need the entire SDK, just the tools which come in a ~11MB zip file).
* Open up a command line and type "adb -d shell". This should detect router as a USB ADB device and give you a root shell.

* The security code is stored in plaintext. Type "cd /var/volatile/tmp", then "cat check_simlock_security". It should show you an 8 character code (usually random combination of letters and digits).
* Type this code in the "/hidden" menu found above.
* Hey presto:
View attachment 683241
You can now use the router with any SIM.
I can also post more screenshots if my instructions are not clear enough.
Enjoy!