Change hasVoicemailNumber to getVoicemailNumber

Bug: 20223485

Change-Id: I67eb12e2030ec8f73326ade4eb750b0c2f6e52ad
diff --git a/telecomm/java/com/android/internal/telecom/ITelecomService.aidl b/telecomm/java/com/android/internal/telecom/ITelecomService.aidl
index d2030f2..35db97f 100644
--- a/telecomm/java/com/android/internal/telecom/ITelecomService.aidl
+++ b/telecomm/java/com/android/internal/telecom/ITelecomService.aidl
@@ -121,9 +121,9 @@
     boolean isVoiceMailNumber(in PhoneAccountHandle accountHandle, String number);
 
     /**
-     * @see TelecomServiceImpl#hasVoiceMailNumber
+     * @see TelecomServiceImpl#getVoiceMailNumber
      */
-    boolean hasVoiceMailNumber(in PhoneAccountHandle accountHandle);
+    String getVoiceMailNumber(in PhoneAccountHandle accountHandle);
 
     /**
      * @see TelecomServiceImpl#getLine1Number