info from My Account ( it gives the option to change the dd date, but you can't do it online)
To change your Direct Debit date, text us for free on 0753 305 1809 ** between 7am and 11pm Monday to Friday, 8am and 8pm Saturday to Sunday.
Changing your Direct Debit date will also change the start date of your monthly package. This means the first bill you receive after moving your Direct Debit date may be higher than usual as we'll need to align you to your new billing cycles. Your subsequent bills will return to their normal amount after this.
Just so you know, we can only change your Direct Debit date on your existing bank details and your balance must be cleared before you can change your date. Also, you can only change your Direct Debit date twice in a 12 month period.
Unfortunately, if we've already finalised your bill for this month, you'll have to wait until we've taken this payment before you can change your date.
Dave
The Service you do for others is the rent you pay for your room here on Earth - Muhammad Ali