You order an eSIM for Belgium on the internet, you receive a QR code, scan it, follow the fondamental steps and within less than 2 moment you have année eSIM installed on your phone. Data-only means that incoming or outgoing calls/sms are not supported and these eSIMs from Airalo do https://www.becharge.be/be-nl/Kopen/betaalkaarten-PCS-Belgium-2-152