[HELP]Unlocking Sony Xperia M4 Aqua bootloader [HELP]

Hi people of XDA,

I'm looking forward to unlock my phone's bootloader, but unfortunately in the service menu, the status of my phone says "Bootloader Unlock Allowed=NO" :(

Is there any way to change the "NO" to a "YES"?

Additional informations:

1. My phone is SIMLOCKED to a carrier
2. I have the 16gb model (E2306)
3. I have already contacted Sony, but they can't do anything :(

Thank you very much!

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