I'm sorry to hear that you're experiencing issues with your Oppo Find X2 lite while roaming in Singapore. It's possible that there may be some network compatibility issues between EE and the local network providers in Singapore.
Here are a few things that you can try to troubleshoot the issue:
Manually select a network: As you mentioned, you can try manually selecting a network on your phone by turning off the auto-select option in your network settings. You can then select a local network provider in Singapore and see if you can connect to their network.
Check your APN settings: Access Point Name (APN) settings determine how your phone connects to the mobile network. You can check your APN settings in your phone's settings and make sure that they are set to the correct values for EE. You can usually find these values on the EE website or by contacting their customer service.
Reset network settings: Sometimes resetting your network settings can help resolve connectivity issues. You can do this by going to Settings > System > Reset options > Reset Wi-Fi, mobile & Bluetooth.
Check with EE customer service: You can contact EE customer service and inquire about any known issues with roaming in Singapore. They may also be able to assist you with troubleshooting the issue and ensuring that your account is properly configured for roaming.
In terms of accessing your texts online, you can try using a messaging app that supports online messaging, such as WhatsApp or Telegram, to complete your verifications. Alternatively, you can try accessing your text messages through a web-based messaging service, such as Google Voice or Skype.
