Chances are no. You will have to wait from the day you changed over. You needed to change your before april 1st, to keep your old date. They might be able to do it, but you might have to call and beg.
If you are changing your plan only to get the upgrade, you are better off taking the difference and saving it.
Single person plan the difference is like 20 dollars a month. If you take the 20 a month for the next 7 months that is 140 dollars.