Matrix Tracker

Was a client for Matrix for over 3 years (stand to be corrected) in January lost my car emailed them to stop the deductions with Fidelity as well as l had 2 trackers on the car ...Fidelity stopped but been struggling with Matrix since l've retorted to reversing the debit every month twice and every reversal is costing me FNB saying they close it but Matrix keeps on changing reference on the 15th this month they double debited...I don't know what to do..They also call me and l tell them same story