They're all computer dialled, as already mentioned if not on your contact list, don't answer and when rung off, block and report the number.
You can register here for landline and mobile blocking calls.
https://www.tpsonline.org.uk/tps/whatiscorporatetps.html
There's one scam going around Sussex at the moment, where a 'roofing expert' calls phishing about loft insulation and purporting about condensation.
My mother law had this call the other evening, which did catch her at first, but quickly realised what it was.
Received a call on my mobile yesterday, from this number, 0203 270 7048.
Informing me that HMRC had issued an arrest warrant, for monies that were overdue.
I'm currently on the run, disguised as a :shit::lolol: