The most common cause for an error being returned whilst registering a domain , is due to an incorrect phone number format.
As per the error you will recieve, the format of the phone number should be as follows: +44.2031294400
It should...

• ...start with the country code, prepended with a '+'rather than '00';
• ...have a '.' (full-stop/decimal) separating the country code & the main number;
• ...omit the first '0', as is standard when dialing international numbers;
• ...not contain any spaces.

If you are recieving a different error, or continue to have problems with the format of your phone number, email our title="Support">Support team.