For people who have come back from a trip Abroad like myself and just got Public Mobile for the first time and their data isn’t working. I have a solution that worked for me when everything suggested did not. First step is to go into any VPN that you may have used and disable it in the app. If that works then you don’t need to do the following steps. The next step after is to go into your Settings > General> VPN & Device Management > VPN and make sure the VPN Status says Not Connected. If it is connected and you try to disconnect it but it keeps reconnecting, the next step is to look at the Device VPN which would be right below the VPN Status. In there you will find one or more options with a check mark on one of those. The check mark does not matter because you will be doing the following step for every option available in there. The next thing you will do is press the information button (blue i that is in a circle). You will then disable connect on demand for all of the options on the Device VPN list. After that just disconnect from the wifi that you are connected to and try to use your data. It should work after that. If you do want to use a VPN you will only be able to do it on wifi and not your phone data. Every time you activate your VPN you will need to do all of the steps again.
If there are any questions I will do my best to answer them. I sadly do no own an Android phone so I can not answer any questions for that but my assumption is that it is the same problem for Android
