Change hasVoicemailNumber to getVoicemailNumber

Bug: 20223485
Change-Id: Iadab72029e67f30edce6f9ccbc2680fbd229c201
diff --git a/system-api/23.txt b/system-api/23.txt
index 1284e12..0d34dcf 100644
--- a/system-api/23.txt
+++ b/system-api/23.txt
@@ -30262,9 +30262,9 @@
     method public java.util.List<android.telecom.PhoneAccountHandle> getPhoneAccountsForPackage();
     method public java.util.List<android.telecom.PhoneAccountHandle> getPhoneAccountsSupportingScheme(java.lang.String);
     method public java.util.List<android.telecom.PhoneAccountHandle> getRegisteredConnectionManagers();
+    method public java.lang.String getVoiceMailNumber(android.telecom.PhoneAccountHandle);
     method public boolean handleMmi(java.lang.String);
     method public boolean handleMmi(java.lang.String, android.telecom.PhoneAccountHandle);
-    method public boolean hasVoiceMailNumber(android.telecom.PhoneAccountHandle);
     method public boolean isInCall();
     method public boolean isRinging();
     method public boolean isTtySupported();