From the Cranbrook Town Council Facebook page:

“E.ON ENERGY SERVICE CHARGE
Your Town Council recently brought a matter to the attention of E.ON that their annual energy service charge not changing other than by inflation contradicts the residents’ Customer Supply Agreement. Following our initiative, E.ON have now reviewed what the residents have been charged up until 31 March 2016, against what they would have been charged up to the same date, had they priced your energy service charge in line with inflation. We understand that residents will receive a letter stating how much has been credited to their Heat account and if you are affected by this you will receive a credit on your account in July.”