Answered question
Dear Fizz.
So I am near to get level 3 and I don't want to have a voicemail, do I have any option?
What happen when I don't want to have a free voicemail?
No reward other than that, don't use it if you don't want voicemail
Other answers
Upgrade is granted to you when you reach certain level. It's up to you to decide to apply that upgrade or NOT to your plan.
If you don't want voicemail then just don't apply it.
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Keeping them slots open for future better upgrades!!