It looks like you can buy a SIM card in Cuba, e.g.,
https://suenacuba.com/tourist_sim_card_cuba/how_to_get_cellular_internet
You could ask Gail if you could have (or buy) her phone for the trip, on
the assumption that it's unlocked after all this time (you'd have to
check).
If not, you could buy an unlocked phone on eBay:
https://www.ebay.com/b/Unlocked-Flip-Cell-Phones-Smartphones/9355/bn_99612323?LH_ItemCondition=3000%7C1000%7C1500%7C2010%7C2020%7C2030&_sop=15&mag=1&rt=nc
> From: robert <http://dummy.us.eu.org/robert>
> Date: Wed, 27 Nov 2024 09:58:56 -0800
>
> If you really need a cell phone, you might buy a burner before you go.