Try these options
Try restarting your phone (Restart your iPhone, iPad, or iPod touch - Apple Support), and if that doesn't help try settings/general/reset - reset network settings. You will have to re-enter Wi-Fi passwords, but won't lose any data.
If you are having trouble with saving your phone number when messaging or facetimeing, go to Settings >Messages>Send & Receive. In the "You can be reaches" section, there should be a check mark next to your phone number.