It's possible to inject a
fake number into the system and I'd be prepared to bet that's what's happening in your case.
Firstly, UKPhoneInfo.com (which is usually reliable) lists '023 89' as 'designated', meaning that it's been put aside for future use:
https://www.ukphoneinfo.com/023-code-allocations
Secondly, I've just tried calling that number and the code isn't recognised as a valid one.
So the call is probably coming from an overseas scammer. (They frequently use fake numbers to make it look as if they're calling from the UK).