How can I make a payment for a minimum fare?

At any Servicaixa ATM of CaixaBank.

At FGC Customer Assistance Centers, depending on the line you are traveling on:
-On the Barcelona-Vallès line, at the CAC in Pl. Catalunya station.
-On the Llobregat-Anoia line, at the CAC in Pl. Espanya station.
-On the Lleida – La Pobla de Segur line, at the Balaguer station.

You can check the opening hours, location, and request an appointment at link to https://www.fgc.cat/atencio-al-client/centres-presencials/

You can also make the payment electronically using the barcode through Caixa Oberta at: https://www4.caixabank.es/apl/pagos/index_ca.html