I have the iPhone 4s on cricket wireless and had an unfortunate event happen while listening to voice mail messages. I decided to setup a password while in the main menu, because we all know about the good security practices, and how easy it is for others to listen to your voice mail if no password is setup, by spoofing your phone number.
Anyways, I hit the option to setup a password and the call was disconnected before I was able to enter in a new pin number. No big deal right? So I went back in to the voice mail system, and I was prompted for my password!?…I tried the obvious defaults like 0000 and 1234…but neither of these worked. I then went to http://www.mycricket.com/ and logged into my account thinking I could reset my password from the web, no luck…the only way to reset your password (according to their website) is to call their tech support line. So, here I go to call the tech support line. When I explain I need to reset my voice mail (which seems like a simple thing to do) the Customer Service Rep informs me that by doing so I would lose all my current voice mails! I told him not to do that and asked what the default password was, he explained that I could try 0000,1234, or 9999.
I hung up and tried the last one I did not try which was 9999 and that worked! So if anyone else is struggling with the default password for cricket voice mail, hopefully this will help you.