T-Mobile released an OTA for Galaxy Note 5 and S6 Edge Plus that fixes call failure issue

Galaxy Note 5 and S6 Edge Plus on T-Mobile getting a new OTA firmware update. This is a minor update that fixes the random call drop issue on both devices, the update comes as build number N920TUVU4EQE1 for T-Mobile Note 5 while G928TUVU4EQE1 for T-Mobile S6 Edge Plus. The update is based on Android 7.0 Nougat that has already been released for these devices.

If you are a user of above mentioned devices and faces the call failure issue on the previous build simply install the OTA on your device it will fix the issue. The update not only brings bug fixes but also brings other minor improvements in the firmware, so keep your device tuned to receive the OTA, go to Settings >> About device >> System updates.

Install N920TUVU4EQE1 build on T-Mobile Note 5

Just install the previous firmware on your device by following this guide and then give a try to OTA System updates.

Install G928TUVU4EQE1 on T-Mobile S6 Edge Plus

Also follow this guide to install the firmware and then give a try to OTA System updates.

Source: T-Mobile (1,2)