Is it possible to determine if the SIM/Phone number has changed?

Question

We have a product where the user registers by providing their phone number.

However after they register they could potentially change their sim.

Is it possib

Answer 1

Yes, of course it is possible. Link CoreTelephony.framework to make following code compile:

CTTelephonyNetworkInfo* info = [[CTTelephonyNetworkInfo alloc] init];
CTCarrier* carrier = info.subscriberCellularProvider;
NSString *mobileCountryCode = carrier.mobileCountryCode;
NSString *carrierName = carrier.carrierName;
NSString *isoCountryCode = carrier.isoCountryCode;
NSString *mobileNetworkCode = carrier.mobileNetworkCode;

// Try this to track CTCarrier changes 
info.subscriberCellularProviderDidUpdateNotifier = ^(CTCarrier* inCTCarrier) {
        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"User did change SIM");
        });
};

By values of mobileCountryCode, mobileNetworkCode, carrierName, isoCountryCode you can judge about presence of SIM. (Without SIM they become incorrect).

There is also some undocumented functions/notifications in CoreTelephony, but your app may be banned by Apple if you'll use them. Anyway:

// Evaluates to @"kCTSIMSupportSIMStatusReady" when SIM is present amd ready; 
// there are some other values like @"kCTSIMSupportSIMStatusNotInserted"
NSString* CTSIMSupportGetSIMStatus(); 

// Use @"kCTSIMSupportSIMStatusChangeNotification" to track changes of SIM status:
[[NSNotificationCenter defaultCenter]
    addObserver:self
    selector:@selector(SIMNotification:)
    name:@"kCTSIMSupportSIMStatusChangeNotification"
    object:nil
];

// This one copies current phone number
NSString* CTSettingCopyMyPhoneNumber()

Addendum Another possible (and legal) solution: if your company has a database of phone numbers, you can send an sms or call(and cut) any specific number to verify that user still uses the same phone number.

UPDATE Function NSString* CTSettingCopyMyPhoneNumber() doesn't work anymore (returns empty string).