OK to call mobile carrier for unlock AFTER root?

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http://androidforums.com – Hi, I want to root my phone so I can use mobile hotspot. However, I am afraid to do it because after I've used it for 3 months, I can call T-mobile to unlock it so I can use the phone overseas when I go on vacation. I am afraid that if I root my phone, T-mobile won't be able to unlock it for me or they will find out and refuse to unlock it. Has anybody called T-mobile up to unlock a phone successfully after rooting it? I have a Samsung Galaxy S II and T-mobile. Thanks, :) (General)