Since the Nokia C2-00 relies heavily on Nokia's legacy servers for OTA updates, and with the discontinuation of 3G networks in many countries, the OTA feature may fail or report "No Updates Available" even if your software is old. In this case, you must use Method 2.
If the official servers are unresponsive, enthusiasts often use "Phoenix" to manually flash the firmware files. Nokia C2-00 Latest Software Update Download