Three
This number is listed by Three on its own website (Customer services from any other phone).
Source: “From any other phone Call us on 0333 338 1001” (opens in a new tab). Checked 14 October 2026.
This could still be a scam call
Criminals can make their number look like a genuine one (this is called spoofing). If someone calls from this number and asks for money, bank details, a code or passwords, hang up. Then call Three back on a number you've found yourself, such as the one on their own website or on a letter or bill from them.