EWON. With an N. the are pretty good, but slow. Like months slow. Have you tried talking to your retailer? They should be able to look at your history and see that that bill is really unusual. Also check your meter reading with what is says on the bill. That will be a good indicator. And don't pay it until it's sorted out. If you lodge a case with EWON, they can't disconnect your power for non-payment over this dispute while it's being investigated.