Craft 2 CMS - How to change Limits in Dashboard
If the account you're using has admin rights you could do so by going to:
Settings > Fields > [Field label of your service display] and edit it. On the bottom there should be a input which sets the limit of your displays to 3. 

You should only check with the person who build your website if they didnt set the limit in the code to 3. If so he has to change that.