Giffgaff says it’s already paid back any overcharged customers whose records it held between June 2016 to June 2018.
It says it’s been trying to contact customers who have left Giffgaff to give them a refund, but if you haven’t heard anything you can check whether you’re owed using its web tool.
Giffgaff also says there are 1.4 million customers who haven’t been refunded for the period between May 2011 and May 2016, because it no longer holds their records. Their refunds, worth over £750,000, will be donated to charity.
But if you think you’ve been overcharged during this period, you can still get in touch with Giffgaff with any bills or records you have of your account from this time.
You can complain by calling 0330 041 4802, sending an email to its complaints department or writing to Complaints, Giffgaff Ltd, Belmont House, Belmont Road, Uxbridge UB8 1HE.