In keeping with modern times, Giffgaff must start accepting crypto currencies as payment. Bitcoin is the most well known, but their charge high fees. Dash charges low fees and super easy to understand https://www.dash.org . Crypto currencies are vastly trusted and used by financial institutions and military services. It also helps communities - Venezuela was the country which most used Dash crypto currency in February 2019.
Members will benefit by having an extra option on how to pay for their giffgaff phone services and handsets. Many members already use crypto currencies.
Giffgaff should implement my idea because it is 2019 and because it is important to make the lives of your customers easy, by accepting crypto currency payments - all crypto coins, not just Dash.