MTN South Africa are just ********** 😡😡😡😡

.I took a contract of 24 months for data on 2018 and it ended this year on April..I did phone MTN on the 1st June 2021 to cancel and the lady I spoke to said she canceled it...Last week I was very shocked to receive a Call that they took my name to credit collectors that I owe them R1630.00 but how cause I did call and make sure I canceled the contract?...I also Remember the name of the lady i spoke to and also have a Ref number