I've moved your post from the natter section (the staff don't usually check that forum) and merged it with your original thread regarding the Volt speed This should bump the post again, but I agree you should have had answers and a solution by now.
It's a nuisance having to answer security questions but they are there for a purpose, for your own protection, and protection of your data. You wouldn't want someone to get hold of sensitive information about yourself, such as say medical records or payment details, or make changes and tie you into a new contract etc.
Companies have to follow the DPA process by law, if they don't they can be fined a huge amount, or even have their licence removed.
I have worked within call centres for various companies and failure to ask security questions can result in instant dismissal for the agent.
One of the companies I worked for (I won't name them but they were an energy company) were under investigation due to DPA failure and were severely at risk of losing their licence. Due to this the company insisted on every agent performing DPA , even when passing the call between agents, and the transferring agent advising that the customer had passed DPA. It was frustrating for us as call handlers, and even more annoying for the caller. I agree with performing DPA again for cold transfers, but not for warm transfers, BUT the caller could still have been passed the phone to a non account holder in the time between the agents passing the calls between each other.
It's frustrating for agents as well if a customer rattles of their name, address, account number etc before being asked for those details. Why? Because the agents then can't accept those details as answers to security questions, because they haven't actually asked them, and must then find other questions/methods to determine that the caller is the actual account holder.
(apart from some agents not performing DPA at all, or accepting incorrect answers, one of the reasons the energy company were being so strict was because a caller had put a complaint into the ombudsman that the company allowed changes to be made to his account without his authority - he had completed DPA and then passed the phone to his wife and the agent hadn't asked for the account holders authority for his wife to speak on his behalf, nor asked the account holder to confirm he was happy for the account changes that his wife had asked for to be made, so he wasn't very happy with his wife or the outcome of the call)