O2 UK Warns Mobile Customers Over New Inactive SIM Scam - ISPreview UK

If O2 contacts you about an inactive SIM, ring them back on the number on your bill or their official website — never use a number from the message itself. Crooks are banking on you panicking about losing service; don't let them.

Stop and think before you act. If something feels urgent, threatening, or too good to be true — that urgency is the weapon. Scammers use pressure to override your judgement. Nothing is ever so urgent that you can't take five minutes to check, call back on a number you found yourself, or ask someone you trust.