That is almost certainly a scam @vick1, as O2 do not "cold call" customers.
The way forward is described in many threads on this community, such as :-
Solved: Fraud ? - O2 Community
https://community.o2.co.uk/t5/Pay-Monthly/Fraud/m-p/1588633
In particular :-
Block the number and do not follow any links.
Forward the scam text to 7726 - It's free.
Other ways to report here including Action Fraud website
https://www.o2.co.uk/help/safety-and-security/phishing-and-smishing-advice
How to block a number:
https://www.samsung.com/us/support/answer/ANS00062352/
https://support.apple.com/en-us/HT201229
O2 never text from a mobile number.
If you think you’ve been the victim of fraud – whether that’s because you’ve given details to someone over the phone, or clicked on a link in a suspicious text or email – there are things you can do:
Contact your bank if you think you may have given out financial information. They can help protect your account and stop transactions
Change your account and online account passwords
Forward fraudulent texts to us for free on 7726 and we’ll look into them
Contact Action Fraud on 0300 123 2040
Call your Virgin Media or O2 customer services number if you think somebody’s taken out a contract with us using their details
Virgin Media customers can phone 150 from their landline or 0345 454 1111 from any other phone.
O2 customers can call 202 from their O2 phone or 0344 809 0202 from any other phone.
Please also remove the link to stop others clicking on it.
