T-Mobile will have its 3G network sunset in July 2022 and has informed Quectel. Since Quectel’s LTE Standard EC25-A modules have the Ue_Usage_Setting, which basically tells the network what's more important for that UE (voice or data) configured as Voice Centric if the user device does not support VoLTE after T-Mobile’s 3G sunset, the network service of the device will be shut down by then. Therefore, T-Mobile requires Quectel and its customers to modify Ue_Usage_Setting from Voice-Centric to Data-Centric when performing T-Mobile certification and actual network use. Browan has taken necessary precautions and will have new firmware in order to avoid cellular disconnection if you are using a T-Mobile SIM card.