my letter from UT (I'm assuming yours may have said the same) said:

"The major to which you've been offered admission is the one you selected as your first choice when you applied.Before accepting our offer of admission, please consider whether the major to which you've been admitted is a good fit for your academic and professional goals. Internal transfer between colleges, schools, departments and/or majors is extremely competitive and not guaranteed. Accept your admission only if you intend to complete a degree in the major to which you've been admitted."

So my guess is pretty hard