Could this be the same person in the last post here?
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Getting a mobile phone in England
Excerpt:
The minus in buying the SIM card while in GB is you don't know the number that will be assigned to you, so your friends will not be able to call you. I think a better idea is to buy a global SIM card, which will serve you in UK and other countries. Some of them has no expiration at all, so it is yours for life. I know SimCardGlobal.com Cheap International dual SIM cards and free global roaming has a good service with cheap price, and they have a branch in Australia. You might want to consider it.
RoadRunnerUS
Phones: Xiaomi Mi Mix 2, Samsung Galaxy A50, ASUS zenfone 3,
Sim cards: AT&T (Contract), 3 UK, Piranha Mobile