Pay the full bill when you can
The full amount is the default payment option on the bill; paying it keeps you out of the rotativo.
If you can't, compare the options on the bill
The payment-alternatives area lists financing options with monthly and annual rates and the CET, ordered from the lowest total cost.
Ask for the DDC
The Documento Descritivo do Crédito shows your original debt, interest charged so far and how much more can still be charged under the 100% cap.
Consider portability
You can move the card debt, including amounts already in installments, to another institution, and the original creditor can't charge you for the portability; the BCB says the process can take up to 7 business days.
Escalate if the numbers look wrong
Contact the issuer's service channel and ombudsman (ouvidoria), and if unresolved, register a complaint with the Banco Central or a consumer body.