Issue with phone number

Question

I recently got a new phone and a new number and had to delete my old number off of my account, then I proceeded to register my new number. When I tried to sign into my account for college it said "calling your phone" but it was my old phone number then I tried it again and it came up call or text both my old number. I'm really confused on why this is happening after I redid it over and over again and really need to get into my account for college.