A big +1 to what ONELABEL has said
A reputable publisher will work on a split of the proceeds from the song
Alarm bells would be ringing if a publisher was asking for a fee!!!!
Are you sure you don't mean a song "plugger" or a pitching service that will help you pitch your songs?
There are lots of these around that charge a fee (ie Audio Rokit, TAXI, SongLink etc.)
I am not sure how you could do a "split" deal with these though without losing a % of your publisher rights, which may make you less attractive to the actual publisher!