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I successfully unlocked my iPhone SE over a year ago but recently cannot use roaming data from my current provider EE. Although I can still make and receive calls an error message appears when I try to go online. I suspect some elements of the Vodafone software are still embedded that may be interfering with the new provider. Is there any way of checking this out?
It won't be any network bloatware or software as the iPhone is one exception as Apple don't allow Vodafone interference in their iOS.
You could have the phone looked at via an Apple Store Genius Bar.
As a process of elimination can you try your sim card in another phone and also check your network app or account to ensure no roaming bars are activated and also check the connection settings in the iPhone too.
Current Phone > Samsung Note 9 _512Gb > Model: SM-N960 Hybrid-Duos.
Samsung Gear s3 Frontier Watch.
If the phone has been unlocked over a year ago and working perfectly until recently, this will be a network issue at your network providers end and you will need to take this up with them at account level.
If you post on the EE Community forum they will advise further and you should get a good response from the EE Community.