APN problem and mobile data

Returning from a trip abroad, my Canadian Public Mobile service stopped providing mobile data.  The problem was that the APN parameters for Public Mobile had been erased. And the "edit" and "add" options for APNs was now disabled.  Only entries for TELUS and Koodoo appeared, and neither were suitable.
I found this solution,

• https://forum.xda-developers.com/showpost.php?p=75157321&postcount=14

and it worked.

NB: on the phone

• turn "USB tethering" off
• enable developer mode (system/aboutphone/7 taps) and switch on USB debugging
• make sure you use a good USB cable 

  Here's the text of that post at https://forum.xda-developers.com/showpost.php?p=75157321&postcount=14

This Works for 8.0 and 8.1 Devices

I came up with a new way that solves this issue.....no root required

I have confirmed this working on two Android 8.1 devices that use Verizon MVNO's (Pixel XL and Pixel 2 XL)

1. Turn phone off
2. Take out sim card
3. Boot phone up
4. Enable usb debugging and connect to PC
5. open up an ADB shell (if you dont know how to do this then do some research)
6. enter the command

Code:

am start -a android.intent.action.INSERT content://telephony/carriers --ei simId -1

7. This will open the "Add new APN" activity.
8. Fill in all the APN info you need to and name it whatever you want and then click save in the the menu options up top.
9. Once you save the APN...turn the phone off
10. Insert SIM again
12. Turn phone on and let it boot up.
11. Go to Access point names in settings and select the new APN you added.

Have a good day