IC System review: paid bill is stillmarked as unpaid

I had recently sent a check for the amount of 186.62 for an overdue bill that was due to Petsmart. This collection agency cashed my check yet it still remains unpaid on my credit report.I sent the check on Sept 11th 2009 . As of Oct. 4th 2009 it was listed as unpaid. Collection agencies do nothing but try to bleed you dry. This is extortion to say the least . If you don't pay them there money they report you to the credit bureau. I can not believe the credit bureau believe these low lifes