OnePlus released a changelog for the OnePlus X Oxygen OS 2.2.0 OTA update:

Manual mode for Camera AppSave to SD card option in Camera AppUSSD bug fix for IndiaAdded dual SIM preferences back in system settingsOTA App upgradeSecurity patchesGeneral bug fixes and optimizations

Update highlights

The USSD bug fix is the main change in this update. Due to this bug, OnePlus X users in India were unable to check calling/data related information after the end of a session. For example, when you end a call on a prepaid connection, Indian carriers send call cost reports containing call duration and call charges. Checking your remaining talktime or data balance was also not possible due to this bug. The Oxygen OS 2.2.0 OTA update has finally fixed this on the OnePlus X. Additionally, OnePlus X users can now save photos to memory cards directly instead of transferring them manually. The option to save to SD cards is now present in the Camera app settings.