If you want to get phone number the same way as one can do in the Swift code, you can do it like this:
val contact: CNContact = CNContact()
val labeledValue: CNLabeledValue = contact.phoneNumbers() as CNLabeledValue
val phoneNumber: CNPhoneNumber = labeledValue.value as CNPhoneNumber
val number: String = phoneNumber.stringValue()
This piece of code is incorrect as far as I do not initialize contact correctly, but the idea is to cast elements of the List, received from the phoneNumbers() function.