Grant Mercantile Agency Debt Collection Complaint

Grant Mercantile Agency Debt collection department,

Cont'd attempts collect debt not owed Debt was paid California

I had old water bill accounts from city - ca water department.bac in 2010 I work out I payment plan with bill from the billing department.i paid all old accounts off .and I got a letter from grant mercantile collection agency.telling me I still owed those bills I paid to city -.i told them I have paid these accounts off.and im infect in good standings with them .I also ask they confirm this info with bill give them his info.since then all I keep getting is old bill information I also dispute.it with credt companys.the information they recvied from grant mercantile is wrong and aginst the fair cedit act