The first thing to try is another mains socket, just in case the one you’re using has developed a fault.
Then try another usb cable and/or mains charger of the same voltage and output capacity (ie 2000mAh).
If you’ve proven that the mains socket, charger and cable are ok then inspect the charger port on the phone, does it lock intact with no debris in there?
After you’ve confirmed, to the best of your ability, then assuming how old the phone is (less than 12 months old) and it was purchased direct from iD, it would be advisable to pop it down to your local Curry for them to have a look at it.