Thank you for reaching out to us. We appreciate your interest in knowing if Galaxy Note20 5G (AT&T) works in the United Kingdom. We apologize; this phone is AT&T phone locked. Contact provider (AT&T) for details about unlocking the phone.
For your reference, an unlocked phone works on multiple networks, and make sure that you have a compatible SIM card. SIM cards must be compatible with the area's available networks. International calling, data services, and coverage vary by the network provider.
You may visit our website for more information about unlocked phones: https://www.samsung.com/us/mobile/phones/unlocked-by-samsung/.
Should you need more assistance, please feel free to get back to us via the following options:
1. Facebook Messenger: http://m.me/samsungsupport
2. Twitter: https://twitter.com/messages/compose?recipient_id=18768513
3. Samsung Community: https://us.community.samsung.com/t5/Samsung-Community/ct-p/us
Reference #: 1144246031
Have a great day.