Also, I know you mentioned that this started occurring after the last update but have you checked for a more recent update to your phone's software? I'm a person that I don't believe in wasting money and at this point I've come to the conclusion I'm wasting money for a service that's doing no different than there competitors.
But that's good for a few hours at most and then once again my call goes straight to her voicemail.
Here are the major wireless carriers contacts.
Select Cellular, choose Cellular Data Option.