Old debt

 I had a cell phone thru bluegrass cellar. To keep in Comtact with my dying mother of cancer.in 2008. I had my phones taken from me when we took her to St. Louis. I turned in my phones as being stolin and a month later I received a bill for $6500.00  I was shocked and again called them as they told me Iam liable for this bill after a lo g time of arguing and being transferred from one person to the next. They told me it will be taking off and that the phones was t shut off right away.  Well 2yrs later my wages was garnished and after being taking out of my check for a couple yrs my job ended. They  never garneshed me again. But they have called me and I once again told everything. They agreed to mark it up as pd in full.  However it's still on my credit report to pay $7200.00. What can I do.