frieda97 It says “the number you called is not recognised”
OK. You need to fill out a report form, as only an agent can recover a lost number in the way you described.
In the first line give the agent your full lost number i.e. 07*********** which no longer works.
Also give your current number and the approximate time and date it changed.
Confirm you did not request a number change.
Give your current email that you can access associated to your giffgaff account profile.
Replies will be shown here ⤵️
and update agents as the report progresses