To change a member's payment method away from BACS:
Members>members details>membership tab:
Then go into the contact record from the 'member' tab:
Once in the contact record screen, click on the 'Bank Account Details' tab and untick the modules selected for BACS:
Save all these changes. To check that this member won't be included in the BACS run, open the direct debits collection via BACS screen (Accounts>Direct Debit Collection), click on 'add unpaid to list' and check member doesn't appear in the list: