Locked to unknown network

[gsausalito]

Hi:
I've bought a Sony Xperia Z locked (supposedly to Movistar Spanish network) but it's locked to
an unknown network because i tried several sims (from vodafone, movistar, yoigo...) with no luck.

Is there any way to know what is the operator locking the phone so i can unlock paying for a unclock code using
its imei?

Thanks for your time!

 

[gsausalito]

Really? No one?