what happens when you switch formulas my daughter on Neosure but her doctor said she gonna take her…

what happens when you switch formulas my daughter on Neosure but her doctor said she gonna take her off it come June cause that when we go back to the WIC office and have to have the paper saying either her doctor put her on regular infant formula or still on Neosure I wanna be prepared even though we still got 2 months on Neosure