Debit order date changed without my concent

Yesterday I received an email stating my credit card debit order date was changed. I phoned FNB to enquire, however after numerous calls and being sunt from one department to another i gave up. I then tried again and the consultant advised me that they send a sms upon i had to respond and if i dont respnd they automatically change the date without the client concent. In my case it was changed to 23-05-2019. Pay pay date is 25-05-2019 as per my agreement i signed with them. I would like to know how they came to the conclussion that it should be on the 23rd if im getting paid on the 25th. Debit is going off tomorrow and there probably won't be suffient funds. who is going to be liable for fees of returned debit, since all of this was done without my concent.