Caller asked to enter 10digit mailbox number

[Beckid]

I recently bought iPhone 4. Now I can't access my voicemail. I'm asked to enter a mailbox number. And callers to my phone are asked to enter a number also.. What's wrong?

[Leiko27]

Have you tried opening voicemail by hitting the phone button then selecting voicemail? Adding an iPhone to your account resets your mailbox, by the way.