Hi there, take a look at this guide.
Good = These phones are in perfectly usable condition. They’ve lived a good life and they’re fully functional with only some minor wear and tear. For example Think of your friend who uses their phone all the time. Someone who might toss their phone in a pocket or handbag with their keys while they’re out and about. They’re not too worried about the odd mark as long as the phone works.
Very good = These phones are in very good condition. You can at least tell they’re pre-owned. But only if you look closely. Think of your friend who keeps their phone safely wrapped in a case but isn’t too bothered by the odd light scratch. A few superficial marks are possible around the edges of the phone. These phones have lived, but it’s been an easy life.
Excellent = these phones look practically brand new. They’re in great condition with no marks or scratches on the screen. This is the phone owned by your friend who treats it like their baby. They've probably popped on a case and screen protector 10 seconds after opening the box and they never took it out. These phones are so close to new you’ll be hard pressed to tell the difference.
If you’re not happy with the mobile device you receive giffgaff give you up to 14 days from the received date to send it back to giffgaff and claim a full refund.
Complete return instructions can be found here https://community.giffgaff.com/t5/Solve-your-questions/Phone-Return-Instructions/ta-p/10441537