Devisting from loan agreement

I have a loan with Capitec and every month I will get a sms saying that my next installment will be collected earlier the month. This is making things very difficult for me since I gave them a date for the installments to be collected on the same date every month , but instead it is being collected way sooner than stated on my loan agreement. That is breach of contract from the bank's side so I honestly do not appreciate the fact that they are deviating from the agreement we both agreed upon.