Newly installed PLDT FIBR internet connection but can't access most sites including 192.168.1.1 (shows no internet connection when connecting on my android phone)

I recently just put up a business in Angeles, Pampanga. I just had my PLDT fibr 200mbps installed last December in the commercial bldg and I'm seriously annoyed by its performance. I can access some websites like FB, Ig. I can even play Mobile Legends on it. The problem is that I can't access most websites including NBA(to stream), modem settings(192.168.1.1),youtube etc. I can't even change my modem settings because it won't let me connect on it lol. I would make a ticket before and they would close it without confirmation, saying that the problem is already fixed. Sometimes I can access NBA on my laptop but never on my phone. Any idea on how to fix this permanently?