You can select which field Synci should base payee information on. Most banks include this in the sender/recipient fields. This setting is available under Source > Advanced > Payee field.
You can check out the values of the available fields by clicking "Details" on a transaction. Every field we have received from the bank will be available under the "Details" and "Advanced" tabs.
If none of the available fields are giving usable information, you can disable payees completely by disabled Source > Settings > Set payee.