Please help - P45 informing me my new style ESA ‘ceased’ last week

I’m going out of my mind as this morning a p45 for
my ESA claim arrived with no warning and no letter of explanation.

When I migrated to the UC last year I was told I was also being moved to the new style ESA. I completed a new ESA commitment meeting by phone and was told that £600 and something pounds would be deducted from my UC as I was now going to be getting the new ESA payments.

I’ve tried calling DWP on the number mentioned on the letter they sent me last May to find out why I’ve got a P45 and what to do next but I can’t get through.. I keep calling, go through the automated verification process and each time after about 20 minutes, the line cuts out. I’ve called 4 times already as it’s the same thing each time.

I’ve left 2 messages in my UC journal as don’t know what else to do and presumably, I’m hoping that if they are no longer going to pay me my ESA, my UC should increase as they were deducting those payments.

In my UC account it says if I stop getting a benefit (eg ESA) to tell the people I claim it from to update their records that I get UC but how do I do that if they don’t pick up? And surely they’re already aware as it was the the ESA people that told me I was moving to UC and would get the new ESA payment in my last comes from them last year?!

On the P45 it tells me to let DWP if there’s a change to my income, but they’re the ones that have just told me my allowance has ceased. So am I supposed to call and tell them too?!

Really panicking as I am due 2 more ESA payments before my next UC payment next month and have no clue how I’ll manage without them.

Please can somebody help. Has this happened to anyone else? Is it a mistake?