Don't fall for it thinking it's free money. Installment Pix is basically a loan the bank pulls from your pocket later, with interest baked in. The trap is that it seems harmless because you're just tapping a button, but over the next few months that money gets deducted straight from your account every month. And interest rates for splitting up Pix payments tend to be high, like 3-5% per month depending on the bank - that's a hefty rate. The real danger is splitting up several things without keeping track and waking up owing money all over the place.
Only use it if you really don't have another option and you know exactly how much you're gonna pay in the end. Like, do the math: that 500 reais Pix split into 12 payments could easily end up costing you 600, 650 reais. Is it really worth it? If you'd just saved up the money over two months it would've been cheaper. Now, if you're going through something one-off and you know you're gonna have the cash to pay it without squeezing, fine, but that's way different from splitting everything up because "it fits in the budget."
The truth is this service works well for people who have discipline and not for people who are already tight on money. If you're already doubting it, that warning sign matters - it probably isn't for you right now. Better to save it for an emergency instead.