My mobile phone operator has confirmed that I have unlocked my Iphone, but I still can't use other carriers. When I put in the SIM card, I am prompted that my SIM card is invalid or does not support the SIM card. He suggested that I seek your help
iPhone 8, iOS 12
Your carrier has not unlocked your phone. Apple does not unlock phones.
How to unlock your iPhone for use with a different carrier - Apple Support
Your carrier has not unlocked your phone. Apple does not unlock phones.
How to unlock your iPhone for use with a different carrier - Apple Support
Help with the activation
