Sinch Callout Verification : not verifying on input "1"

Question

I am trying to use Sinch Callout Verification for my iOS App. I have implemented the code according to documentation. And I do receive call on iPhone. Recorded voice tells me to "Please press 1 for verification or hang up if you didn't requested this call"

When I enter "1" from my iPhone keyboard, nothing happens. Computer just keep repeating above message.

But when I hang up I do get a call back in my code with failure.

Below is my code :

    NSString* defaultRegion = info.countryAbbr.uppercaseString; //this is my country in upper case and its correct
    NSError *parseError = nil;
    id<SINPhoneNumber> phoneNumber = [SINPhoneNumberUtil() parse:[info getFullPhoneNo]
                                                   defaultRegion:defaultRegion
                                                           error:&parseError];
    if (!phoneNumber){
        // Handle invalid user input
    }
    NSString *phoneNumberInE164 = [SINPhoneNumberUtil() formatNumber:phoneNumber
                                                              format:SINPhoneNumberFormatE164];
    id<SINVerification> verification = [SINVerification calloutVerificationWithApplicationKey:@"4ecb3c90-6d92-40c5-9a96-649f84fcc93e"
                                                                                  phoneNumber:phoneNumberInE164];


    [verification initiateWithCompletionHandler:^(id<SINInitiationResult> result, NSError *error) {
            [SPProgressHud hideAllHUDsForView:self.view animated:YES];
            if (result.success) {
// when I enter/press "1" call should hang up and code here should run
            } else {
                if ([error.domain isEqualToString:SINVerificationErrorDomain] &&
                    error.code == SINVerificationErrorCancelled) {
                    // Handle cancellation error code separately
                    NSLog(@"Verification cancelled: %@", error);
                } else {
                    // Inform user of error, e.g. that input was invalid.
                }
            }
        }];

• iOS Version : 11.2.6
• Xcode Version : 9.2
• Sinch Verification Version : 2.0.6 installed using cocoapods
• Language : Objective - C
• Country : Pakistan (PK)
• Service Provider : Zong (CMPak)