You don't have to say good or bad, lazy or even ugly. Just say... I contacted him / her on xyz date. I had not received a response by abc date. I contracted with Albestboat work on and was promised a completion date by xyz. The work was completed on mnop date. No need to bad mouth anyone but by stating the facts then there is no bad mouthing and people will know. With out their name, or area of coverage or specifics no one can follow up and learn from your experience.

My 2 cents...

Ciao