Naudoju lauko "mob_number" tikrinimui toki skripta, bet meta klaida, kodel? 
Kas negerai?

if(preg_match("/^+?(07[0-9]{9}|447[0-9]{9})$/s",$_POST['mob_number'])) {
$mob_number = escape_data($_POST['mob_number']);
 } else {
  $mob_number = FALSE;
  echo '<p><font color="red" size="+1">Please enter your mobile phone 
number!</font></p>';
 }