New Style Commitment phone call for UC

Hi there I am an appointee for my son who received his letter for migration from ESA Support group to UC and I did an application form with Citizens advice helping me fill it in on 18th August. Today just had message in journal for telephone app on 15th September for 30 mins. It says AGREE A NEW STYLE EMPLOYMENT AND SUPPORT ALLOWANCE COMMITMENT.
So worried what does this mean will he still be in Support style group or does it mean he might lose it. Also he won't be able to speak much he'll be too scared can't I speak instead please. I'm so worried it's all gone wrong

Hi David I did ring Cit advice he said it looks like Andrew been on old ESA long time and goes onto new style ESA because of his contributions as well as UC is that right? Will I be able to talk to them as his appointee please.
Is this normal that you have to have UC and New style Esa

Hi can you tell me can I ask that Andrew doesn't do New style ESA just do UC? It's complicated having to do 2 claims and payments.
IS THAT ALLOWED or will it mess up his UC claim would the UC want to assess him again to see if he goes into LCWRA group as he was in support group?
That's my worry will UC not put him in LCWRA automatically if he doesn't do ESA
Sorry it's so confusing we thought it would just be migrate over to UC
Thanks for any advice I'm so worried what to do as his mum and appointee