CB ESA and notifying DWP of an occupational pension claim

I am (belatedly) claiming my occupational pension whilst on PIP and CB ESA. I believe my ESA will be adjusted by a small amount and I will then qualify for a small.tax bill (the pension is very modest). Does anyone have advice on the best way to notify the DWP? I was thinking guaranteed next day delivery signed for letter rather than trying to hang around on the phone for hours or days.

Any advice welcomed.

i am on cb esa and i recieve a pension,
ijust phone them up each year to tell the of the rise in my pension, what should hap[pen is the first 85 quid of your pension weekly will make no difference to your esa, anything over 85 pounds a week is halved and taken off your esa, so if you get 95 quid a week pension, your esa will reduce by 5 pounds