How can i choose whether i want to send as an iMessage or SMS

When i send someone a message that has an iPhone as well it automatically sends it as an iMessage which is fine. But alot of people i talk to dont have iMessage on while using there mobile data so they dont see the message. I was hoping there is a way to choose what format to send it as. I know you can choose to send it as a Text Message afterwards but i want it where i dont have to switch iMessage on and off all the time, so it will send as a text message automatically