There are a variety of ways in which your credit may have been used without you realising it:
- Sending MMS (Picture Messages), which cost 16p each (24p if sent outside the UK) and are not included in any GoodyBag allowance
- Calls and texts to numbers outside the UK, or premium rate numbers (such as 0870) which are not included in any GoodyBag allowance
- Calls to another GiffGaff number which went over 60 minutes, or your free calls allowance may have expired (dial *100*1# to check this)
- Data usage by apps running in the background (apps often install with automatic updates turned on by default)
- One or more of your GoodyBag's allowances may have been used, resulting in subsequent charges coming from your airtime credit (dial *100*7# to check this)
- You purchased airtime credit instead of a GoodyBag, meaning all of your usage has been chargeable. You can verify this in your purchase history on your 'My GiffGaff' page.
If none of these seem to be applicable, you should contact an Agent at https://giffgaff.com/support/ask/incorrect_balance
and they should come back to you within 24 hours.