Been overpaid childcare vouchers - can employer rectify it?

[Helpmeltb]

I submitted a request to reduce the amount of childcare vouchers I get (dd1 probably won't need childcare after this term) and it should have been effective from this month's pay. However it looks like payroll haven't bothered changing it (New hr system may be to blame) so I've had £80 more deducted than I should have.

Can they sort it? Will it have to wait until next month?

I have asked them but not had a reply yet and thought someone might know.