One way:

c:\@Work\Perl\monks>perl -wMstrict -le
"my $phone = '(777) 1234-0000 RAM:007';
 print qq{'$phone'};
 ;;
 my %xlate = ( '(' => '',  ') ' => '-' );
 ;;
 $phone =~ s{ ([()][ ]?) }{$xlate{$1}}xmsg;
 print qq{'$phone'};
"
'(777) 1234-0000 RAM:007'
'777-1234-0000 RAM:007'
[download]

Update 1: I know, I know, the next thing you're going to ask is "how do I handle any number of spaces after the closing paren?"

c:\@Work\Perl\monks>perl -wMstrict -le
"my @phones = (
   '(777)1234-0000 RAM:007',   '(777) 1234-0000 RAM:007',
   '(777)  1234-0000 RAM:007', '(777)   1234-0000 RAM:007',
   );
 ;;
 my %xlate = ( '(' => '',  ')' => '-' );
 ;;
 for my $phone (@phones) {
   printf qq{'$phone' -> };
   ;;
   $phone =~ s{ ([()]) \s* }{$xlate{$1}}xmsg;
   print qq{'$phone'};
   }
"
'(777)1234-0000 RAM:007' -> '777-1234-0000 RAM:007'
'(777) 1234-0000 RAM:007' -> '777-1234-0000 RAM:007'
'(777)  1234-0000 RAM:007' -> '777-1234-0000 RAM:007'
'(777)   1234-0000 RAM:007' -> '777-1234-0000 RAM:007'
[download]

Update 2: Another version of the substitution that does not depend on a translation table and is more flexible WRT area code format:
    $phone =~ s{ \( \s* (\d{3}) \s* \) \s* }{$1-}xmsg;