Have you checked your blocked caller list?
Does it work if they dial the number manually @JB1930 ?
Can you get them to delete you as a contact and try it?
Please note, this is not customer services and we cannot access your account. Do not publish personal details (email, phone number, bank account).
Link to our guide on how to contact them can be found here
Track usage, upgrade and get support with the My O2 appDownload My O2