Is there any way to "Unload" credit for a Lisbon Viva Viagem card?

On a recent trip to Lisbon (Lisboa), I made use of the local public transport system. For many (maybe all?) journeys, the only way to enter and pay for the journey as a vistor was using a Viva Viagem card, purchased from either a ticket office or (more likley) a ticket machine.

This card could be charged with either single-journey tickets, credit, or day passes. For my first charging with credit, at the end, all credit was used up and on recharging the ticket, any of these options was avaialable. However, the second time around, there was €0.15 left. As I was leaving Lisbon soon, and the credit expires after a shorter period than I thought would take for a new visit, it would be cheaper to add a single journey, rather than charging with the minimum amount of credit. This option however was not available from the ticket machines due to the remaining credit. On consulting a customer services operative, they insisted the only option was to buy an entirely new Viva Viagem card and charge that up with a single journey.

Now, as the card only costs €0.50, this wasn't a big deal, but it was somewhat frustrating. Is there really no way to dump this small amount of excess credit?