AFAIK there are neither hidden nor secret settings.
I have raised a case with the agents three times over my five years of membership and all three cases were fully resolved to my satisfaction inside 24 hours.
Over a year on, there is still confusion with the June 2017 EU roaming directive
If you are roaming then virtually all calls between EU member states are included (but please see the notes below).
BEFORE YOU LEAVE THE UK
From 20th September 2018 To make things a little easier all giffgaff customers are given a 14 day grace period during which they are able to 'Roam Like At Home'.
However, if no prior UK usage is detected giffgaff will sendan SMS asking you to submit proof of UK residency in order to remain eligible.
To set up EU Roaming.
Nice and easy, all that you need to do is enable roaming in your giffgaff profile, if it is not already enabled,www.giffgaff.com/buy/topup
to make international calls / send texts).
2. The EU regulation does not apply to free giffgaff to giffgaff calls where the 'calling' phone needs to be in the UK; the regulation only applies to calls which are normally charged.
3. The EU regulation does not apply to use on-board ferries or cruise ships.
4. The EU regulation states that it is designed for 'occasional' use and cites a maximum period of 60 days roaming use in any four-month period.
As stated above. you will get a maximum of 60 days inclusive roaming after which you will be on PAYG rates (although these actually reduce to 3.2p per minute 1p per text and 0.060p per MB data if you still have an active goodybag).