This is an account issue which you need to raise with an agent rather than us on the forum.
As you are probably aware, agents can take upto 24 hours to reply although are often much quicker. Agents would be able to check your account history and resolve the problem if giffgaff are at fault (which it appears they may be).
Use this link and explain in as much detail as you can. You may not be able to complete all sections on the link, so explain your query within the comment/further information box