Palisades Collection L rip-off, false claims Bethlehem Pennsylvania

I was formerly a member of AT&T wireless services. When Cingular bought out the company I proceeded to discontinue my services with AT&T and joined the Cingular network at that time. AT&T continued billing me for months after I requested that my service be discontinued. I called when I recieved a collections bill in the mail and was not offered any assistance with the account but instead offered methods of payment. I have now seen this delinquent mark on my credit reports as of late and need to know how to go about getting this off of my credit report.

Joseph
Los Angeles, California
U.S.A.