DWP ESA errors anxiety

I receive contributions based ESA. The amount I receive is reduced because I get two ill health pensions (both from the same scheme). I have been in this position since 2016. Everything ran okay until last autumn when payments were missing or days late. When I spoke to ESA they told me this was because there was too much information on my file and some needed to be archived.

My second payment in January came in at an increased amount. I phoned ESA to query this and was told it was correct. Still concerned about an overpayment I wrote a letter to them and posted it on 2 February. The amounts continued to come in too high. Then in April, this increased again due to the annual increase. I have not received my annual letter with a breakdown of the amount. I tried phoning in several times but couldn't get through. Eventually, I got through last week. I was told my letter was scanned onto the system but hadn't been actioned.

The lady on the phone told me:

It looked like only one pension had been included in the calculation.
The person doing the calculation was responsible for checking it was the same as my previous payment.
If I was underpaid before (I wasn't) I would have received backdated money.
It was a DWP error.
Someone would phone me within 72 hours to sort out the issue.

I haven't received a phone call. Should I write to them again to cover my back? I am worried after seeing the stories about carers being prosecuted for DWP errors.