If you are locked out of your account it means that you had to many unsuccessful attempts. Wait an hour and then when trying to sign in , click on forgot password or username , whatever you have forgotten. Reset it from there.
As for changing your plan you can do it when ever you want but remember that you will loose what ever benefits and credits you have left on your current plan if you do so before your anniversary date. So what ever plan you are switching to , you will have to pay the price of that plan up front. You will have to do this even if you just paid your currebt plan fee that day. So say I paid my old plan today ( June 5, 2019 say $40 plan) ) and want to change my plan tomorrow ( June 6, 2019 to the $50 plan) you would have to pay the price of the new plan . So in those 2 days you would have paid $90 . So it is best to change your plan on the anniversary date ( or as close as possible ) of your current plan. This way you are maximizing your bang for your buck.
Cheers .
