Searching with WebAPI

I have made a web API class for my Customer model. I have the standard methods (GET, POST, PUT, DELETE). The problem is, I want to implement another GET method which is a search. Something like this:

[HttpGet]
public IEnumerable<Customer> Search(string id)
{
    var customers = customerRepository.Search(id);
    return customers;
}

The search method performs a search based on the account number of my customers, using the .Contains() method.

The problem is, when I navigate to: mySite.com/api/Customers/Search/123 I get a 404. What am I doing wrong here?