How to unlock AT&T HTC One A9 to use Wi-Fi hotspot?

Hello, 
i'm new in here. if I make any mistake on writings, please forgive me.
I fall a problem. My HTC one a9 have no access of wifi hotspot. I then communicate with HTC with chat-room, they said that if i'm not in AT&T network, i will not be able to use wifi hotspot. 
So, I decided to unlock the phone. Then boot unlock the phone using one of thread in this xda website. then I successfully unlock my phone. Then I goto HTC website and download RRU for unlocked HTC One A9 v:2.18.617.10 . but when i want to install that ROM, i found error 132: signarure error(not signature error). then again communicate with HTC, they said that i cant install that ROM, that rom is for officially unlocked phones.
I search for 20 hours just for unlock the option "wifi hotspot" but cant find any good help. please help that i want to use my ONE A9 full featured with no boundings.
Thank you all developers.




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