Long ago scammers discovered that they could trick domain name owners into paying grossly inflated fees for domains they already owned. They would send official looking letters to domain name owners telling them their domain name was about to expire and to pay immediately to avoid losing their precious web site address. In many cases the inflated fee was paid without checking.
As companies/owners have become more wise against this they are now trying another approach. A colleague's client had a phone call from "the uk domain registrar" warning them that another company is trying to register all the alternative TLDs for his domain. This means that although the client owned hiswebsite.com this other company was about to register hiswebsite.co.uk, hiswebsite.org etc.
The caller kindly offered to secure all the domians for him before it was too late for a small fee of £800.
Firstly the real domain registrar would never call you to warn you of a similar domain to one you own is being registered. Considering you can buy these domains for £2-£10 each it is clear the £800 fee is extortionate.
This scare tactic and out right lying is just the latest tactic in the spammer/scammers box of tricks.