Bad service

Last month they debited me a day late and blocked my account. I changed my payment date to the 25th to avoid problems. They didn't debit me. They debited everyone I know on the 1st May and again didn't debit me. Now they have blocked my account. I have been sending endless emails to support requesting assistance and there's no response. Their accounts department is *********** yet they penalize me for their carelessness. I called their call Centre l, they promised to call me back and assist. But no one has called me. How can they penalize me for non payment when it's a debit order transaction. Wow