Is roaming free in Brunei with my UK, US, or EU SIM card?

No, absolutely not. Brunei is explicitly outside the scope of most standard EU, UK, or US domestic roaming plans. Major home carriers such as AT&T, Verizon, T-Mobile, or the UK's Vodafone/O2 will likely charge you their highest 'Rest of World' international roaming rates, which can be very costly, often upwards of $10-$15 per day. HotelESIM offers a much more economical and predictable solution, ensuring you stay connected without incurring exorbitant charges during your stay.