Contract Change

I called tracker to compare prices. I was informed by staff that it is possible to reduces my monthly subscription to R 190 a month I agreed and the changes where made. At the end of the month an amount of R400 was deducted from my bank account. I then requested a itemised invoice, but none of the staff members at tracked could help. I also enquired how the new contract with tracker differs from the one I already have but not constructive explanation was given. I am seriously concerned about my security as there are no positive explanations