Me too. I'm on the $50 unlimited plan. I just started my second month and had to get a new phone. Activated the new one with my existing number and this crappy announcement started on every outgoing call.
Contact customer care at 888-294-6804 and ask them to set your announcement level to Low
You can do this from the automated prompts when you call 888-294-6804: (no need to talk to a person)
Then choose LOW from the available choices, this disables the pre-call notifications.
Thank you, very much.