Telephone assessments

Hi
I now have a date for my review assessment. It will be on 4 June and over the phone. I intend to let them know ahead that I want the assessement recorded. But how do I also record it my end, knowing that I wll be using a mobile phone? What are others' experience of putting the mobile on loud speakers and using a separate digi recorder? Would that work? Would it be accepted?
I am really keen to have this "conversation" recorded as I'm 99.9% sure I will be rejected and want to use any misinterpretation examples etc. as part of the mandatory review (that farcical excercise...). I've been there before, hence.
I am so stressed, as you can imagine. I sent the review form just over a year ago and I don't expect the whole process to end for another year. I am really not sure I can get through this, again. The last time was awful.