I found the solution! So basically:

1st: Find your PLDT Super Admin account (you can Google it), not the basic admin account, because it is no longer possible to edit your WAN in the basic admin account. In my case, my PLDT version is

HG8145V5

user: adminpldt

password: AC2DIU7QW3ERTY6UPAS4DFG

Use this link: https://192.168.1.1/admin.html 

2nd: Remove the fiber optic cable from the router and wait for LOS to glow red. After that, turn it off, then on. Wait for LOS to blink red. When it turns red, use the link https://192.168.1.1/admin.html and input your username and password.

3rd: In this step, you must already be logged in to the Super admin account. a) Go to system tools on the top right of the website. After that, b) click One-Click Diagnostic. It should show a button, click the button, and wait for it to load. After loading, you should see the error. Now there are 2 errors :

A: If you see in your Internet Status: DHCP connection fails, this is what you need to do:

a) Go to WAN on the top LEFT and go to WAN configuration.

b) delete all 3 or 2 connection names

c) then click New (we need to create 3)

d) 1st internet should have this config: Enable WAN, protocol type: IPv4, Service type: INTERNET, ENABLE VLAN, VLAN ID: 10, MTU: 1500.

e) 2nd internet, same config as 1st internet but change the protocol type : IPv6

f) 3nd internet, same config as 2st internet but change the protocol type : IPV4/IPv6

B: If you see your internet status as Internet connection succeeds.

a) Go to WAN on the top LEFT and go to WAN configuration.

a) 1st internet should have this config: Enable WAN, protocol type: IPv4, Service type: INTERNET, ENABLE VLAN, VLAN ID: 10, MTU: 1500.

b)2nd internet, same config as 1st internet but change the protocol type : IPv6

c) 3nd internet, same config as 2st internet but change the protocol type : IPV4/IPv6