MFC go back on agreement

HI after arrangement was done and except is every month changes done on my account. It Last month deduct double this month deduct more. Extra difference is paid as arrangement was done. How can we trust the arrangement if finance is doing what ever they want. We are struggling with covid our lifestyle is already on the breadline payment is done as arrangement was done. Why is this happening? Am o suppose to live with less food That I really need?