How to get the user’s country calling code in iOS?

Import Statement :

#import<CoreTelephony/CTCarrier.h>
#import <CoreTelephony/CTTelephonyNetworkInfo.h>

you can get country code for the current Carrier using CoreTelephony framework:

CTTelephonyNetworkInfo *network_Info = [CTTelephonyNetworkInfo new];
CTCarrier *carrier = network_Info.subscriberCellularProvider;

NSLog(@"country code is: %@", carrier.mobileCountryCode);

//will return the actual country code
NSLog(@"ISO country code is: %@", carrier.isoCountryCode);

Apple Docs