The reference on the contact screen is a system generated reference. This is not something that you can amend, as it is an internal reference, which links to that contact in the database. This is also sometime known as the contact ID.
The reference that you can use to search in the system, is the Mandate Reference, or the Alternative Reference. Both of these can be viewed by going to ‘Collections>Mandates’.
The Mandate Reference is what you setup for the customer with their bank, so that you can collect Direct Debits.
The Alternative Reference can be used as your own internal reference for the customer, which you can then search for on the PT-X software.
These can be setup/amended on the following screen (Collections>Mandate>select the mandate):