I changed my phone number and the directions to activate it did not work.
just restart the phone. if that doesn't work for whatever reason go to Settings > General > Reset > Reset Network Settings. (doesn't delete any info, but you will need to connect the WiFi again)
if it's 3G phone dial *228 and select option #1 for programming
if it's a 4G phone simply restart the phone and give it a couple minutes to reprogram itself to the new number
Thanks
Is iPhone 6+ 4g
thank you for posting this, totally helped!