when does change occur once you notify Verizon of your intent?

[scififan2]

Hi! I have been notified that June 24 is my cut off date for the Verizon switchover. I am in the process of switching to Gmail,  but it is a long process and want to retain my Verizon email as long as possible to get everything right.

My question is hopefully simple. Once I click on "I will use another provider" will it immediately lock me out of Verizon email, or will it give me until June 24? Thanks for any help!