Neha (throwing the pack on the pathway arrogantly)- Hey Meg!
Meg (annoyingly) - Hey, Neha I don't understand why you do that always? Don't you know this will harm the environment!
Neha- Huh? Why're you being serious?
Meg- You see if someone will just come and throw trash in your home will you feel good?
Neha- No, of course not, Why?
Meg- Then? Isn't the earth our home? Earth is where we live, you
shouldn't litter it, should you? Moreover the street is also where our home is there, this litter will make it dirty and spread diseases.Plastic will harm the animals who consume it too!
Neha- I understand now, I'm really sorry. I understand this will harm our environment. Sorry.
Meg- Good that you understand. Don't do that ever again.Now put that in your bag and throw it in the dustbin at home.
Neha- Uhm, Meg? I want to do something so that I can pay for all the dirt I've caused in the environment.
Meg- Oh! Well, I say you join the Swachh Bharat Abhiyan campaign at school. You can go on rounds for cleaning public places and streets and moreover whenever you see anyone littering streets just tell that person not to do so and throw it in the dustbin. Understood?
Neha- Thanks Meg! I'll always remember this lesson and also join the campaign. I'll do whatever possible for keeping the environment clean!

This was just an example of you can do that.I know not that long..but you can add your own ideas and creativity to make it better.Remember the best comes when you write things with your imagination.All the best. Hope it helps you! 

Have a good day. :)