Credit was damaged after I cancelled account

I had a wireless account [Edited for privacy.] (Puerto Rico) for 3 years - always paid on time, I then cancelled the contract(by phone)  because I was going on someone else's account.  I was not told about having a balance on the phone when I cancelled and come to find out, they reported me to the credit bureau without being told or receiving a bill.  What do I need to do to get this of my credit report?????  Its only $102 and if I have to pay it I will but I want reassurance that the entry be removed from my credit report.  Thank you.