You can change your regular repayment date in your online account. This will slightly change the interest that you’re charged in the month the payment is moved, as interest is charged daily. If your new repayment date is earlier than your scheduled repayment date, then the interest will reduce. If the new repayment date is later then it will increase.
E.g. If your current repayment date is the 11th and you wish to change it to the 1st of each month, you would be charged 10 days less interest for that month.
If your payment date is the 11th and you wish to change it to the 21st of each month, you would be charged 10 days extra interest that month.