SARS is not consistent and consiradate

SARS informed me that I m owing them which I do not disputed then I made arrangements of R200 every month but to my surprise they decided to garnish me R500 starting in April. My question is that who decided for me to pay R500 ? cos I don’t have the 500 hence I made the arrangement, they did not even bother to inform me that they will be garnishing me. It’s not like I did not stick to the arrangements. The consultant I spoke to was rude m giving me incorrect information that the garnish started last year . I am not happy because with the little I have I do try to stick to the arrangements.