Hi WHUTTH,
I wonder if some of your contacts are not using iMessage and need to chat with SMS. If so you need to use Continuity.
Connect your iPhone, iPad, iPod touch, and Mac using Continuity - Apple Support
To use Continuity for SMS and MMS with your iPhone and your Mac, iPad or iPod touch
- Your iPhone, iPad, and iPod touch need to use iOS 8.1, and your Mac needs to use OS X Yosemite.
- Sign in to iMessage on your iPhone, your other iOS devices, and your Mac using the same Apple ID.
- On your iPhone:
- Go to Settings > Messages > Send & Receive > You Can Be Reached By, and add a check to both your phone number and email address.
- Go to Messages > Text Message Forwarding, and enable the device(s) you would like to forward messages to.
- Your Mac, iPad, or iPod touch will display a code. Enter this code on your iPhone to verify the SMS feature.
Take care,
Nubz