O2 refused to unlock my O2 wifi device from O2 network

[Angela8]

I bought a Huawei Wifi E5573B from ebay but this wifi device is locked to O2 network. It does not work on other network sim cards. Since O2 declined my card payment recently, I want to unlock my wifi device from O2 network and change to another provider. I log in to my O2 account and request to unlock my wifi device.

[Removed]

When type in the IMEI number of my device to some websites for unlocking the device, they can search out that my device is locked to the O2 network. 

Obviously, O2 does not want us to unlock our device from O2 network.

[Enlli]

It needs to be running on an O2 SIM to unlock

Guide: Unlocking an O2 phone to use a different SIM card 

[Angela8]

Thanks for your reply but I am using O2 PAYG sim currently. If I do not unlock the sim, I cannot use other network at all!