Is calling a coyote hard?

My friend and I went by the local wetlands and I thought it would be funny to download a coyote call on my phone. I did so and started playing them out loud and we were walking near the edges of the wetlands and heard something coming towards us. We both backed off, maybe 30 feet and continued listening. We watched for awhile but nothing ever showed. So, is it that easy to call in a coyote?