Interest rate static but interest debit increased

I have an overdraft facility and a revolving credit facility with standard bank and I keep close tabs on all amounts being debited as I am trying to pay these off. The interest, service fee and credit life deductions INCREASED from December to January with no prior notice and in spite of the fact that the outstanding balances on both have decreased. With my OD the interest went up by R6.61, service fee went up by R3.50 and credit life went up by R1.69