Credit Card Manager doesn't require any Internet special permissions, making it safe.

It features a button to generate a spreadsheet file. If you aren't interested in that, you can deny the "Write and read external storage" special permission.

-Write your expenses (name, total value and number of installments) and it will record the value of each installment and the number of installments that are yet to be paid.
-Sort your expenses by name.
-The total sum is in the top.
-Select specific values you want to sum up. If nothing is selected, the total sum will be displayed (by default).
-The 'Advance month' button assumes you paid the monthly installments and decreases their numbers by 1.
-Read the instructions to have a better experience.
-Improve your positive expending habits.