Optimum is expanding its MVNO agreement with T-Mobile to add access to T-Mobile’s 5G standalone (SA) core—while still keeping Optimum’s own in-house mobile core. Optimum says the move will unlock a wider device portfolio (phones, wearables, tablets), improved international roaming options, and new product launches starting early next year after platform upgrades. Optimum ended Q2 2026 with 724,000 mobile lines.