Hi, have you received an email from giffgaff confirming the activation with details of your new giffgaff number?
When you say your phone is saying
When you attempt a call, does it show not registered on network on your phone screen?
Do you mean you don't see your number, balance and goodybag hereHttp://giffgaff.com/dashboard
Has your sim failed to work since you activated the sim
Or was it working initially but then suddenly stopped?