Okay, so I was facing this problem too. After about 2-3 hours of trying to figure out how to fix it. I did it. Hope this helps. My service provider is Criket. I switched the sim card from a Samsung J1 I believe to a Galaxy S6+. Calls worked fine but I couldn't connect to the internet. It keep giving me "unable to establish a wireless data connection lte esm - 27 emm" Something like that. It was from this "RilNotifier" So here's what I did, go to this link "https://www.cricketwireless.com/support/apps-and-services/bring-your-own-device-byod/customer/bring-your-own-android.html" go to the very bottom of the page. On your phone go under (Settings-Connections-Mobile Networks-Access Point Names-Add) Fill out just like how I put it on the bottom. It worked for me. After that I was able to access the internet no problem. Hope this helps. I definitely was happy.
Name: Internet
APN: ndo
MMSC:
http://mmsc.aiowireless.net
MMS Proxy: proxy.aiowireless.net
Multimedia Message Port: 80
MCC: 310
MNC: 150
APN type: default,mms,fota,hipri,supl
APN protocol: IPv4
APN roaming protocol: IPv4
Turn APN on/off: ON