Here's how to fix Charger Not Supported Problem on Nokia C2-03, C2-06, C2-08 Dual SIM phone.
1) Check the battery connector terminals, clean if necessary.
2) Locate the two highlighted components, those are resistors and holds as battery temperature (BTEMP) indicator. Try to replace first the rated 47K resistor then the 120K.
Nokia C2-03, C2-06, C2-08 Charger Not Supported Problem Solution