@Debbie1Do you also have a device plan? as if so 2 direct debits do come out.
If it is a genuine mistake, contact your bank and request a refund under the Direct Debit Guarantee, and they should reverse the incorrect Direct Debit.
Otherwise you will need to persevere with Customer Services
- Xperia 1V - o2 and Spusu
- Pixel 8 Pro - o2 and Vodafone UK