Going to St Lucia

[JohnWil_1664617]

Please can so tell me what setting my iPhone should be on when visiting St Lucia in the Caribbean as last time I went the £15 top up lasted 1hr without using the phone at all. 

[SmartyTrousers]

It's very expensive to use your phone with Smarty in Saint Lucia - around £1,000 per GB of data - and no setting is going to change that.

If your phone supports eSIM, I would recommend getting one for your trip from a provider like Airalo, who charge a much more reasonable £6.50 for a GB of data. You would need to set your phone to use the Airalo eSIM for data instead of the Smarty SIM while you're there. Note that Airalo's eSIMs only include data, not calls or texts, but you can use apps like WhatsApp and iMessage/Facetime instead.

[MSF]

@JohnWil_1664617  When you roam in that country, it is costing £1 per Mb of data i.e. £1024 per gigabyte!!!!

When the phone checked a couple of emails, it probably ate all of your credit straight away.

An Esim is the way to go, as advised by @SmartyTrousers