Terrible customer service. My number port from O2 failed due a problem with giffgaff. Was without my number for over 2 weeks. Customer service is via email chat & they're absolutely rubbish at getting back to you. Was told it would take 5 working days to sort it with the engineers which is ridiculous to sort but it was actually 10 working days. Even then customer services didn't know it had been fixed I had to tell them. I raised a complaint and was treated with scarcasm in their email. Have since ported to Lebara ... half the price for the same deal & seamless transfer.