Extremely devastated

I got a message that I owe SARS more than R7000, which was surprising to me. How can I owe SARS about 80% of my salary because tax is deducted monthly without fail and I don't have any side business. I figured it could be because I submitted days late from the closing date, but still this amount is extreme and I don't know where I am gonna get it from. I went to SARS , they told me to book online, which I did . They gave me a date for 15/12/2020 @14:00. I waited and waited and the call only came at 15:38, it only rang twice, while I was taking out my phone from my pocket to answer, it stop ringing and the person never attempted to call me back till today. I am very disappointed and stressed because really I needed someone to explain to me what the amount is for and get a solution.