giffgaff dont offer a telephone based customer service,everything is done online,it really works effectively but can take some getting used to.
Most questions can usually be answered by the community,so it’s always worth posting your query,in the relevant section first.
The community has some very knowledgable members and problems are often resolved very quickly.
If your problem is account related then you do need to contact an agent,which is very easy choose the topic closest to your query.
Agent replies will be shown here, usually within 24hrs.
Good luck and enjoy giffgaff.