TedKinney,
Answers provided here so far are incorrect or not very helpful. Here is the situation and solution regarding iMessaging with iPhones. This explains more than just your problem. I am providing this info with the hope that it helps others who are having problems with iMessaging\text messaging, especially after switching either from Android to iPhone or from iPhone to Android. It helps to understand what's going on either way.
Apple has it's own proprietary instant messaging system called iMessaging. It is an alternative to the industry standard SMS and MMS text messaging service. And it functions on Apple products ONLY. So, it is only good between an iPhone and another iPhone for instance. It will not work correctly (or at all most likely) between an iPhone and an Android phone because the Android phone doesn't have it. More info at this wiki.
https://en.wikipedia.org/wiki/IMessage
If you have an iPhone and are currently using it with your current phone number, if you want to use Apples iMessaging service (rather than standard text messaging) you have to enable iMessaging on the phone which registers the phone with apple's iMessaging service. It will still send MMS and SMS messages to phones that don't have iMessaging (either Android or iPhones that have iMessaging disabled).
If you are changing your phone number from an iPhone another iPhone you may need to re-enable it on the new phone but probably not if you use the same apple icloud on both phones.
If you are switching your phone number from an iPhone to Android phone YOU MUST DISABLE iMessaging on the iPhone before changing your phone number over to the Android phone. Well, it isn't a MUST actually. It is a "should". It's easier if you do that.
However, there are times that someone is switching to a new phone because their old phone is broken and unusable. And their old (broken and unusable) phone is an iPhone and their new phone is an Android phone. It this case you can't disable iMessaging on the (broken and unusable) iPhone before or after you change the number to the new phone because - Well, the old iPhone is broken and unusable. This will cause you problems on your android phone. You will not be able to send or receive text messages from any iPhone that has iMessaging enabled, which is pretty much every out there.
The reason you can't send or receive text messages on your new android phone is because the phone number that the android phone is on is still registered with Apple's iMessaging service. Those people trying to send you a text message are sending the message through apples iMessaging service and since your phone number is still registered with Apple, Apple is trying to relay it to the iMessaging service on your phone... which isn't there, because it's now an Android phone.
Your phone number is now on an Android phone and has no way to disable iMessaging for your phone number. So, you seem to be stuck, right? Congratulations! You're not. Fortunately, Apple provides the following page which will let you deregister your phone number from iMessaging, even after you've switched to an Android phone.
https://selfsolve.apple.com/deregister-imessage/
And here is more on adding or removing numbers on Apple products.
https://support.apple.com/en-us/HT201349#add
Hope this helps someone.