False Positive Test Of Chlamydia?

I had a pap test done a few weeks ago at a pap clinic and a couple days later my family doctor called and said I tested positive for chlamydia. I took the 4 pills he perscribed me that same day, however, today I received a letter in the mail from the pap clinic saying that they were pleased to say my results came back normal. How could this be?! It would make sense if it were possible for a mess up done on their part because my partner and I have never been with anyone else. Is there such things as false tests for chlamydia?

Thanks!!