@windy259 Hi welcome to giffgaff and the community
•Ideally it takes up to 24 hours for your number to be fully transferred (from the date you've selected to transfer your number weekends not included ).
•In the mean time you can reboot your phone by turning it off and on, hopefully it should work
•After 24 hours, if you're still facing any issues while porting-in your old number on giffgaff so you need to contact giffgaff agents from here ⬇️
hope this has been helpful for