Thanks for that info and choosing the Apple Support Communities. If I understand correctly, you are unable to send an iMessage to another contact that has an iPhone, as it is being sent as a green SMS message on your iPhone. To help with this issue, please follow these steps from this Apple resource on your situation:
If you see a green message bubble
If you see a green message bubble instead of a blue one, then that message was sent using MMS/SMS instead of iMessage. There are several reasons for this:
- The person that you sent the message to doesn't have an Apple device.
- iMessage is turned off on your device or on your recipient’s device. To check if iMessage is turned on for your device, go to Settings > Messages > iMessage.
- iMessage is temporarily unavailable on your device or on your recipient’s device.
Learn the difference between iMessage and MMS/SMS messages.