What a nonsense. I would ask that you recount what you've posted here to customer DOT relations AT flybmi.com; there is every chance they'll be able to find a longer term fix.

If you're avoiding the call centre (and you should) the other option, if you're near a bmi airport and are a regular traveller, is to use an airport ticket desk. These people deal with ticketing all day and are knowledgeable if not always willing to do favours.