Hi I have turned phone on and off , reset all network settings, reset my iPhone X, updated software but keep getting the error cannot connect to network even though 3G shows. What else can I do as I am unable to use my phone currently unless on WiFi
Where did you get the phone from?
Symptoms may indicate a barred handset.
IMEI can be checked here https://www.imei.info/
Unless you are abroad (which you didn't mention) you can use either apn, so I doubt that was the problem in your case.
Maybe just the fact that you reset the network settings in doing so fixed it.
You won't get visual voicemail or wifi calling unless you use the idata apn.