Transferring the major in the same university before first semester


I am Pavan Krishna Ponugoti. I got admit in MS in Petroleum Engineering from Missouri university of Science and Technology for fall 2015. I haven’t booked my VISA slot yet. But I want to change my major from Petroleum engg. to Information of Science and Technology. I contacted the office of graduate admissions and they advised me to start a new application. My question is "Should I apply for VISA using the old I-20(Petroleum Engineering) and then transfer to the course after getting the admit into my new intended program or Do I have to wait until i receive my new I-20(Information of Science and Technology)

Awaiting eagerly for your answer,

Thank you in advance