add a ',' after card value to right conversion to JSON and remove comments at the end
set a instance var PUBLIC_API_KEY, to use when you #import DFConekta.h
Use PUBLIC_API_KEY instance variable of DFConekta instead set public api key in code
Add 'application/json' to HTTPHeader and add PAYMENT_SERVER_URL insance variable of DFPaymentServer
use of PUBLIC_API_KEY and PAYMENT_SERVER_URL