Debiting on wrong date, twice in same month

My policy says that the debit date is on the 1st of each month. But to my surprise we have found that we were being debited on the 13th and 16th. We make previsions in our accounts for the amount which is stated on our policies and for the date which is specified on our policies. Now both times it has bounced, so for both times the bank will be charging a fee because of that. I have phoned Liberty on the 14th, but was placed on hold for such a long time, that I had to give up due to my phone account going up. But strangely, Liberty has still not phoned us, to try and rectify this. Absolutely terrible service.