Changing direct debit date

My current direct debit is the 1st of each month an has already come out for this month but I am wanting to change this to the 26th, will they take a payment on the 26th of this month also?

My experience is yes, if you change the date to later in the month they will take payment twice.

So best change the date on the 26th. There might not be enough time between the 26th and the 1st for the change to take effect, so bear that in mind for next months payment which might still come out on the 1st.