Car taken while payments are up to date/bad servic

As a standard bank client (for over 25years) I feel very disappointed with the treatment I have received from this bank..... I acquired a vehicle through them in 2010 and have never missed a payment. My account was put on arrears due to having paid 900 hundred less than the agreed installment for two months. We then came to an agreement of paying R400 more than the agreed installment to cover my arrears. Documents were sent to me to sign and I sent them back. I received a call from Chantal telling me that she has not received those documents. I resent them and never heard a response from her. I was shocked to see a sheriff coming to collect my vehicle on behalf of the bank without them sending me any notifications. But they continued to receive my payments with the agreed amount. I called Chantal to explain to me what was going on and she told me that she had not received those outstanding documents. I presented the necessary documents as proof that I did send them however I was told this does not prove a thing. I spoke to this two Chantel (Vaf) and Daphney Maphoto who were rude and of no help. STANDARD BANK PLEASE EITHER REIMBURSE MY PAYMENTS OR PLEASE PROVIDE MY VEHICLE BACK.