rollover data when changing FROM $30 to $20 PLAN

[barrykr2]

Hi All. 
My wife and I are both currently on $30 Prepaid Plans and have so much rolled over data that we don't even get in to the bonus data let alone the actual 20Gb.  So the question is: Do we keep our rolledover data if we change to a $20 Prepaid Plan?
Thanks
Baz

[sox2]

A $40 recharge offers Apple Music Streaming Free how is this music activated on my i phone7