You can lock the device to a subset of its supported frequency bands on LTE, WCDMA, or GSM. Note that this operation will result in no service if you prevent the use of all bands that are available at the current location. Conversely, checking all bands is equivalent to No Locking features (that is, no lock applied) and is automatically converted to that setting.
If a cell file is loaded, then for each band, the number of cells on that band listed in the cell file is indicated beneath the band name.
The device cannot be band-locked while a voice call is in progress.