wrong billing or account

there has been a sale of house which is situated at Maclear st 9, vanderbijlpark which was previously owned by Ms SJ MTHUNZI.During the sale of the house, Ms Mthunzi paid R8000 to the municipality for the rates and she was later refunded over R5000. Its been over the year since the house was sold but the municipality is charging her the rates for march 2015 which is R1834.00. she has alredy received a call from one of the consultants who said she must pay within seven(7) days or she will be handed over