I have a couple of customers that are down right refusing to pay and won't return any communications. I have one customer that has no problem calling me up and asking for stuff but has open invoices more than a year old.

I don't take on customers anymore without a signed contract but in general how do you get these people to pay?

Do you use a collection agency? Is it worth highering an attorney? I'm just tired of calling, leaving voice messages and faxing invoices and getting no response...