If admitted into the new program, you will receive a new admission letter to your new program and a new I-20 with the change of program.
You must print and sign your new I-20 once you receive it.
Please note: Graduate program admissions are made on a semesterly basis. In other words, you cannot change a graduate program in the middle of a semester. As a result, to protect your status, your new I-20 may not be issued until after the current semester is over.