I'm on O2.
When I put in my SIM, the Acer seemed to set itself up so I didn't need to do anything APN etc.
However, the voicemail is not setup. I googled o2 voicemail and the number is 901. I can call that and it works fine.
But if I put 901 in Settings > Call Settings > Voicemail a message comes up with "call setting error - voicemail number change unsuccessful"
Anyone have any advice on how to sort this out please?