More from HoFo - as of 5/15/05 you can now request a backdated rate plan and feature (e.g. m2m) changes (upgrade or downgrade). You may only back date to the beginning of the current bill cycle. You must specifically request a back dated change. Unless you request it, a change will occur on your NEXT bill cycle. You must call by midnight ET of the day you want the change to take effect. If you change your mobile number, account number, switch to a different type of play (to/from family, etc.) then you can only backdate to the date of that change.