I have yet to find an acknowledgment by Verizon that a problem does indeed exist with the callback feature with Verizon voicemail. The scenario is as follows: You are checking your voicemail and you press 88# which directs voicemail to call back the number from which the person left the message.
The service used to work with 100% reliability. For the past several months, however, the service fails to dial the number and you wait listening to dead air until you finally realize that it is not going to work. Often, if you hangup and dial *86 to access voicemail again, you will be told that your account has no access to the system. This forces you to hang up and try again.
I would estimate that on any given day, the callback service works between 33-50% of the time. If you do not have unlimited minutes on your plan, this can result in several minutes of lost time per month, as you must listen back through previously heard messages again. Others with whom I have spoken, report similar experiences for those using the service. Verizon help desk will act like they have never heard of this problem, but there is no doubt that a systematic problem exists.