This company has a messed up billing system and their customer service are not giving out correct information. My mum is 85 and was changed from sse to ovo. The first quarterly bill came through in april which was paid and then she was sent 3 demanding / red letters with different amounts on. No bills were sent but she is not even due a bill until the end of July. My mum has recently been ill and has been in hospital so this situation has been very very worrying to her as she has never been in debt. Customer services tell you that ovo do not do quarterly bills but on their website it clearly says they do and they sent us one in April!!