Gear S3 classic with LTE will be available from AT&T starting May 26 - SamMobile - SamMobile
Gear S3 Frontier LTE Review - YouTube
Original Samsung Gear S3 Classic LTE R775S Motherboard
Samsung will soon offer LTE version of the Gear S3 Classic
Amazon.com: Samsung Gear S3 Classic Smartwatch 4GB SM-R770 with Leather Band (Silver) Tizen OS - International Version with No Warranty : Cell Phones & Accessories