The secret is simple: speak Belarusian.
One man shared a story: he received a call from a Russian number offering "free replacement of intercom keys." However, as soon as he said:— Kalі laska, razmaŭliajcie sa mnoj na biełaruskaj move [Please speak to me in Belarusian] — the scammers got confused and hung up.
It turns out that the best antivirus against phone fraudsters is your native language!