Rocket Man (officially titled Rocket Man (I Think It's Going to Be a Long, Long Time)) is a song composed by Elton John and Bernie Taupin and originally performed by John. The song first appeared on John's 1972 album Honky ChÃ¢teau and became a hit single, rising to No. 2 in the UK and No. 6 in the US.
Any replies from iOS devices will show up in the iMessage conversation thread, while replies from non-Apple devices will show up as separate text messages. Any SMS or MMS message will count as an ordinary text message and will not use data.
Considering your usage as you mentioned above I think 20MB of bandwidth would be enough for you. But all will still depend on your usage. FYI: if you want to save on data usage do not use apps that constantly connects and syncs to the internet. Examples of those apps are Facebook, Gmail and other Email apps.