Be polite when you send the email complaint. Use an appropriate word to discribe your problem. For example, use "unsolicited email" or "unwanted email".
They are not spammer. Remember the email you send is to those who handle abuse activity. They are not the one who abused you.
Do undestand especially if you don't get any reply from the domain. It does not mean they have not handle your case. Maybe they are overwhelmed with complaints.
Remember, your ISP ( upon receiving complaints ) has to communicate with other Service Providers/Network Administrators to settle your problem. So it may take sometime to get the reply. Some Service Providers/Network Administrators are a bit reluctant to handle spamming activity.
Say "Thank you" whenever you get the response. Although the response does not specifically mention that they have handled your problem. However, it really depends on you to send the note or otherwise. But of course an appreciation to their effort may just make their day.