Is roaming free in Hong Kong with my mainland China SIM card?

You need to be very cautious about roaming charges when traveling between Mainland China and Hong Kong, or even Macau. Despite their proximity, these are distinct administrative regions with different telecom regulations and often separate network agreements. While some mainland Chinese carriers might offer specific roaming packages for Hong Kong, 'free roaming' is generally not the standard. Using your mainland SIM in Hong Kong without a dedicated add-on will likely incur significant roaming fees. An EastESIM plan specifically for Hong Kong, or a multi-country Asia plan, offers predictable and affordable data, ensuring you stay connected without unexpected costs.