It's just the way your carrier uses to transport voice data during a call, it has absolutely nothing to do with receiving calls.
FWIW I used to receive multiple calls from a British number a while back, reverse searched it on Google and it tuned out to be a barber shop in Bath (!). I've picked up the call eventually, just to explain to this guy, speaking with the most posh accent ever, that I lived in f*cking Venice (Italy) and that if I really wanted to have a cut out of my country I'd go to Austria, or Slovenia, or Germany at most, before considering Britain. He said something like "ah sorry man, my bad, wrong number" and hang up. 😆
@Fishy It's probably just scammers, as far as I know it's not extremely hard to spoof one's caller ID, and scammers frequently use the technique to evade blacklists and such. Just don't answer to those calls and you're good, don't worry too much.