public void setCallingRegions(java.util.Collection<String> callingRegions) {
        if (callingRegions == null) {
            this.callingRegions = null;
            return;
        }

        this.callingRegions = new java.util.ArrayList<String>(callingRegions);
    }
<p>
The countries to which calls are allowed, in ISO 3166-1 alpha-2 format. Required.
</p>

@param callingRegions
       The countries to which calls are allowed, in ISO 3166-1 alpha-2 format. Required.
aws-java-sdk-chimesdkvoice/src/main/java/com/amazonaws/services/chimesdkvoice/model/Termination.java