Default [Q] docomo Xperia A Wi-Fi tethering

Hello guys!

I have a Sony Xperia A (SO-04E) unlocked on a DoCoMo shop. Now I'm using another SIM card, different to a DoCoMo one, but data tethering its not working. The phone is showed on my computer and others Wi-Fi devices, but it's unable to connect to the internet.
Do you have any ideas of what is happening to it?

Thanks a lot!