Loan taken to lawyers after being paid up

My loan was handed over to lawyers some time last year. I contacted the lawyers and paid the outstanding balance in September 2015 and got a paid up letter from them. Today I get a call from a lady by the name of Patricia and she says my loan was handed over in January 2016 to another collection agency. How is this possible when the account was paid off last year?<br> <br> Please can this be sorted ASAP and i want to know what the outcome is on this matter.