That doesn't read right. If they were planning on using the overdraft to cover a cheque, the money was never there - just the option to spend money they didn't yet have.
Some businesses, like football clubs, airlines and ice cream sales are cyclical. You have a lot of income at certain points of the year and little at others. Credit facilities cover the lean times of the year. Barclays pulled the credit on Southampton in April - at the lowest point of the year for clubs (before new season ticket money comes in). If your bank called in your mortgage overnight presumably you wouldn't be problem free?