Contract saga

My name is Sibongile Mahlangu I have a contract with the above mention company the agreement as per contract was they will deduct R91 every week the problem started when I went to maternity they started paying me monthly and the contact started deducting double the amount I went back at work still they deducting double I call and told them what ur doing it’s not part of our contract they said I was in errors yes I agree I was but there is no where in out contract were it state if you fail to pay we’ll deduct double can you please assist ur help will be highly appreciated as these people are doing as they pleases in my acc even deducting on a day we didn’t agree on