As you may have heard TalkTalk has been recently well and trully hit by hackers with millions of their custumer's personal details acquired by the hackers.
My advise to all giffgaff customers is if you have your personal details in auto mode in giffgaff's system then you should revert back to manual mode, meaning every time you add credit you should always input your details manually....every time.
No business/corporation, including giffgaff, are 100% safe from very knowledgeable modern hackers.
Never trust anyone I even go back into Amazon after each purchase to remove card details
Very wise. There's all this talk of hackers stealing stuff but guaranteed something silly was going on TalkTalks end that made it possible for them to get in.