Hi @panik,
The LTE modem only support bands 1, 2, 3, 4, 5, 8, 12, 13, 18, 19, 20, 28 you cannot set the frequency arbitrarily.
None of those are in - or confined to - ISM spectrum.
There is a relatively new standard called LTE-U to operate LTE in unlicensed spectrum (usually coexisting with WiFi at 5Ghz), but we don't support it.