DWP says i didn't inform them about my pension

Hi I apologise if this is repeating myself but not sure if is loading as a question last night. I can't find under unread, as i know you're not open yet.
I only read top line which stated they'd looked at my ESA and no changes. But later in the letter , saying i didn't inform DWP about rise £4 in pension.
I'm on non means tested legacy ESA and I've never had to tell them before
And of course i'm late with the letter which say's 4 weeks
They have been paying me though ?
I do have a big social media account on twitter, and our work through Wow petition/campaign assess impact all cuts disability support. We got two hearings HOC
And now fighting Green Paper
help and advice please
Michelle

Hi you always have to notify them of a change regarding a rise in pension as long as you are receiving contribution based legacy esa.
I have had to do this every year and last year they sent me a derogatory letter saying I hadn't informed them, even though I had.
Shortly after that they sent me a reassessment form (they had left me alone for around ten years)
I don't know whether it was sheer coincidence or whether them making out I didn't inform them of a change of circumstances but I had to go through a telephone assessment.
What a right polava and worry but following the assessment I remained in the support group.