Hello
You're not paying for the Visual Voicemail, it's part of the data plan, and it's required on all smartphones. $40 sounds line a smartphone fee on a Mobile Share plan, is that what you have? When you complete your two year contract, your monthly phone charge will be reduced, the only other way to lower it is to switch to a basic phone.
Please let me know if you have any other questions.
Thank you,
Dmitriy