Foxglove Energy are inept

When we switched to Foxglove Energy they were named Fischer Energy. After a long time I contacted them to ask them when they might bill me. Shortly afterward, many months' bills arrived in the mail, each in its own envelope. The billing has continued to be odd: today I received a bill asking me to pay it within fourteen days of March 28th which seems considerably optimistic on their part. This may continue previous optimism: I suspect they thought it would be reassuring when some weeks ago they sent me unexpected mail telling me that they aren't going out of business.

Update: I now notice that a few weeks ago they sent me a bill dated March 28th with a smaller invoice number for a slightly higher amount. I think they may have tried to revise a previous bill and their system sent out a new one as if the previous had never existed, including asserting a debit balance that ignores my subsequent payment.