IOS app converting the dialed number automatically

I am working on an iOS app and writing code to make calls from that app. It is working fine for non toll free numbers, But for some number such as <REMOVED BY MODERATOR> for BigBasket, it is converting the number as +1(860)<REMOVED BY MODERATOR> which when dialed comes as wrong number. But for numbers starting with 1800 it is working fine. I am searching solution of this query and taking help from some and iphone blogs. If you have answer of my query please reply me. Please check my code snippet.

private func dialNumber(phoneNumber:String) {
let phoneUrl:NSURL = NSURL(string: "tel://\(phoneNumber)")!
let application:UIApplication = UIApplication.sharedApplication()
if(application.canOpenURL(phoneUrl))
{
application.openURL(phoneUrl)
}
self.ratingLabel.text = "Rate (self.selectedProvider!.providerName)' Customer Care"
callCenter.callEventHandler = {(call:CTCall!) in
switch call.callState {
case CTCallStateConnected:
break
case CTCallStateDisconnected:
NSUserDefaults.standardUserDefaults().setBool(true, forKey: "ctCall")
break
default:
break
}
}
}