Changing date of ESA Assessment

All is not sweetness and light however. The latest appointment was cancelled just like the others and luckily I got sent a letter confirming cancellation too, something that doesn't always happen. Then the DWP write to me threatening to cut off my benefits if I can't give a good reason for not attending. They got informed by Atos I'd not attended. I've sent off a copy of the cancellation letter to the DWP and hope they'll accept it. I've rung Atos and got a personal apology from the girl who told the DWP I'd not attended, she says no-one told her the situation. Worrying, all this. I was a bit worried too the Freepost envelope supplied for my reply by the DWP would mysteriously disappear in the post so I asked at the Post Office how I could prove I'd sent it. Turns out the PO have a a method for this so you can get proof of postage even with a Freepost envelope. I thought I'd pass that along!