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When my iPhone mobile call goes unanswered for 15 seconds - the call is not diverted to voicemail (which is set to divert to 121) - rather the caller is advised: "your call couldn't be connected, please check the number & call again".
Is there a code or set of symbols that I can input to enforce the diversion to 121?
The details on how to set your Call forwarding or Diversion is available here: https://support.tpg.com.au/mobile-voice-features#toc_4
Also, the details on how to set or enable your Voicemail is available on the same page.
Let us know how it goes.
BasilDV