I'm getting a non-trivial amount of scam phone calls to the phone number contact listed in WHOIS. Could I change it to a premium rate line? If the scammers want to talk to me so much, make them pay for the privilege!

Seriously though, are there any restrictions on the type of phone number I can give as my WHOIS contact? Notwithstanding that it is a phone number which can be used to contact the domain holder.

In the UK, cell phones are more expensive for the caller to call than land-lines, so I suspect a significant number of people are already listing a "premium rate" phone number.