Hi mandisa292,
The following steps address what you're describing specifically, and should provide a solution:
If you can’t turn on or sign in to iMessage or FaceTime on your iPhone - Apple Support
If you have followed the steps correctly and you still have the issue, let us know if you get any new alerts or error messages when trying, as those may help us determine what might be causing the issue.
We also recommend restarting your device and keeping it updated as those steps assure you have cleared out any minor software issues and are running the most current version.
Restart your iPhone - Apple Support
Update your iPhone or iPad - Apple Support
If you still have questions, reach out to Apple Support directly, as this may require closer guidance: Get Support
Cheers!