Magento 1.9 – Price Doubled in Checkout When setGrandTotal is Applied

I'm creating a module which applies discount based on Payment Method, programatically, everything works fine, until I call setGrandTotal and setBaseGrandTotal, for some reason, they double the price in the checkout page, but weirdly, when the order is finished, the price is correct.

My function:

foreach ($info->getQuote()->getAllAddresses() as $address) {
                $quote = $address->getQuote();
                $quoteData = $quote->getData(); // grand total
                if ($quoteData) {
                    $pixDiscount = Mage::getStoreConfig('payment/pix/extra_discount');
                $quoteData = $quote->getData();

                $totalWithDiscount = ((floatval($quoteData['grand_total'])) - ((floatval($pixDiscount) * floatval($quoteData['subtotal']) / 100)));

                $address->setSubtotal(0);
                $address->setBaseSubtotal(0);

                $address->setGrandTotal(0);
                $address->setBaseGrandTotal(0);

                $address->collectTotals();


                $quote->setGrandTotal($totalWithDiscount);
                $quote->setBaseGrandTotal($totalWithDiscount);

                $quote->save();
                $address->setQuote($quote);

                $address->setGrandTotal($quote->getGrandTotal());
                $address->setBaseGrandTotal($quote->getBaseGrandTotal());


                print_r($quote->getGrandTotal());
                //if (strlen($address->getDiscountDescription()) > 0) {
                //  $messages[] = $address->getDiscountDescription();
                //}
                //$messages[] = $discount['description'];


                $address->setDiscountDescription(
                    "Disconto teste"
                );
                $totalDiscount = 0;
                $totalDiscount = floatval($pixDiscount) * floatval($quoteData['subtotal']) / 100;
                $address->setDiscountAmount($totalDiscount);

                $address->save();
            }
        }

'''

I've tried dividing the results by two (but it affect the price after order is complete). Already debugged every var possible and all of them have the price correctly, I just don't have any more ideas of why this is happening.