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Hi @fionnualat . A8 is on TPG's list of LTE phones.
https://www.vodafone.com.au/support/network/volte?title=android&accordion-id=samsung
Also, LTE is indicated on Samsung specs.
https://www.samsung.com/au/smartphones/galaxy-a/galaxy-a8-black-32gb-sm-a530fzkaxsa/#specs
You may have to contact Samsung for this.