The recommended process is to clear the remittances and then reprocess as follows:
Unallocate the payments from the invoices.
Post a negative value Payment and allocate it against the now unwanted payment.
Reprocess the remittance via the BACS process.
In some circumstances, the payment type can be moved from cheque to BACS. Contact the support team to investigate this option. If you have trouble reaching us, see Get support in Access Financials.