Smart Meter VS DD Discrepancy

My Smart meter verifies that I am using on average less than my budgeted £2 per day - averaging less than £60 per month, so why have bulb decided to up my DD to £84pm. If I cant get a satisfactory answer Ill simply switch to a green provider (which I have found) that will not have this price increase? This isn’t to do with winter consumption as we generally use more power in the summer for Air Conditioning and have little need for heating in the winter. Thx