Ultra high latency

I'm not an expert, far from that, but it seems there is something very wrong with NextDNS. I'm using it in Brazil, São Paulo, and although there are half a dozen servers with low ping (10-20) that show up on ping.nextdns.io, the NextDNS Windows app ALWAYS choses the very worst one. I'm getting pings as high as 350 for google.com and facebook.com. The app seems to prefer "anexia-sao 128 ms (ultralow2)", and I see no reason for this, it is simply unacceptable. I tried messing with configurations and sometimes it goes to a good server, only to go to the worst one in the next few hours. I thought it could be a problem with my ISP, but I even subscribed to Mullvad just to test NextDNS with a reliable VPN. If I set my location to my own city, São Paulo, I immediately get a NextDNS server in... INDIA! Sometimes, if I refresh the VPN connection, I get a good DNS server, but like I said before, that only works for some hours. If I can't get this to work I would like a refund, as I've just signed a yearly subscription plan, but it also seems there is no support, neither the option to ask for a refund. And yes, I've tried NextDNS network diagnostic tool. What can I try to do any suggestions? Thank you for any advice.