Having worked in outbound Telstra Mobiles, If you don't want to give too much info they let you choose a password. If you dont want to tell the password you can tell them 2 forms of ID that they have listed (like middle name and DOB) and they can tell you the password to confirm to you that they are who they say they are. Middle Name and DOB are such easy to get info that they aren't counted if you wanted to open an account as ID on their own, but if you already have the account they are enough to be able to confirm for both of you the correct ID. It is very hard work in an outbound sales centre. They have very high turnover because it is depressing work and the targets are impossible to reach.

The number of times I would get through ID and then tell a customer they were just out of contract for them to say "No-one told me it was coming up" for me to say "That's what I am trying to do" after them giving me the 3rd degree about ID. Often if they are calling you they have something important for you to know, so ID trading is a good way to do it. For example if you said that you are willing to give your DOB and middle name but she will have to give you the address to prove to you that she is who she says she is. When I was there we only needed full name and DOB to ID landlines, but generally they are not under a contract and can be altered any time with no additional charges.