phone call failure or disconnected call backs while making a phone call in iOS

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Mobile

iPhone

iOS

On a button click I am making a call inside my app by using the following code

NSString *phoneNumber =@"telprompt://123-4567-890"; 
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:phoneNumber]];

I want to do some working if the call is failed or disconnected (might be due to low balance or network signal problem). Is there any delegate for call disconnect or failure for doing this? Any help will be appreciated.