I just started my own electrical contractor business (no employees, only myself) and I did a couple of service calls for a company, and afterwards sent them an invoice for $640.00 It's been almost three months, and I still have not been paid. I have contacted their maintenance manager ( the one who called me asking for assistance) and their accounts payable. They don't even return my calls, and I am tired of calling. What's the best way of sending this unpaid debt to collection? Who has to pay for the collection expenses? Please advice. Thanks