Estate agent finder fees

A year and a half ago I engaged an estate agent to find a tenant for me. Somehow they managed to get me to agree to pay just a little bit more for their management service; the fees for their services were charged monthly by invoice. However, halfway through Year 1 I cancelled the management service but the contract said that I had to pay for the full 12 months. I only paid for 6 months at the time. They occasionally ask me for the outstanding balance but I can’t work out why they haven’t written a stronger letter or threatened the small claims court/legal action. Am I missing something here?

If you’re contractually obliged to pay it then they will probably get around to it eventually.