Bills and accounts / Paying your bill / Direct Debit

1. How can I change my Direct Debit details?
2. How is my monthly Direct Debit payment calculated?
3. Can I cancel my Direct Debit?
4. How can I increase or change my Direct Debit payments?
5. How can I set up a Direct Debit?
6. Can I change the date of my Direct Debit payments?
7. How can I change my bank account details?
8. Why have you increased my Direct Debit even though I am in credit?
9. How can I change the bank you collect my Direct Debit from?
10. Can I pay my bill by Direct Debit?