Incorrect refund

My car was paid off on the 28th of April 2021 by insurance based on an amount received from Iemas three days before that. A deduction was already taken from my employer of which the settlement amount did not include it. In May again a deduction went off. I then called an questioned this and five days later I got a refund which was R1 146.58 short. I've sent emails without a single response. My calculation is based on the two installments I paid though my account was already settled. All they did was to reflect the settlement on the date they finally found it instead of back dating it to 28th of April. Had I not raised this I would still be paying.