debt orders

We changed banks and when we whanted to change our debit date were told they don't do debit order for the 2nd of every mounth, so my husband told them to cancell the debit order only to have our account debited on the 30 of June , so when I. Phoned they told me they only do debit ordrers on the 15th and last day of the month, I told them to change it to the 15th only to be told that they will take a payment on the 1dth of July so I said no cancell the reqwest I will phone again after the 15th, Low and behold they debit us on the 15th of July with no money in the acc to cover the debit order. Now they whant to suspend my service for non payment.