So I have an economy 7 storage heaters which can cost a bomb if not used properly. My previous supplier eon based my monthly bill on estimates and the last tenant and threating with debt collectors even though, they know I'm in the middle switching suppliers... However once I phoned bulb up, there was an option to call back (calls to their line free of charge unlike eon) as they were busy. They called back and sorted out the initial readings and evidence I supplied and contacted them right away. I am to contact eon to remind them of this. Great customer service and online portal!