What are the costs for visual voicemail?

Visual voicemail messages use data: Wi-Fi or mobile data. For a 30-second message, this would be 28.35 Kb, or (brace yourself) 0.02835 MB. Which is very little data. If you don't have Wi-Fi or your mobile data bundle has run out:

• for mobile subscriptions: this will incur a minimal out-of-bundle charge of € 0.10/MB on your next payment invitation/invoice, unless you have set the out-of-bundle cost limit to € 0 for that particular phone number. In the latter case, you can also deactivate your visual voicemail and use classic voicemail.
• for prepaid cards: this amount will be deducted from your calling credit