Student loan Be afraid

My son took out a student loan for one year My wife as guarantor We paid this off in December. We asked for a settlement and paid it off in full. We told Standard Bank and to confirm. No answer In Feb - took off the next instalment and a whole load of charges which put him in overdraft!; We went to Northgate branch and were told we had not come into the branch to close it .EVEN though we had sent an mail requesting and giving proof of payment.The branch was told to cancel it.Guess what Standard bank have again deducted the Student loan and again he had no money in the account