Can't access internet. Can ping gateway thou

Hi, my routers DSL and internet lights are green. I looked into my router's status and i am connected to (gateway). PPPOE authentication is OK. Everything seems fine. But i can't access internet. The only computers i am able to ping is my gateway other than that i can't access anything (not even DNS). Here are diagnostics result.

I will appreciate if any PTCL guy could help me here. I left a complaint and all they did was call me after a day or two asking me if am still disconnected. The costumer service is poor as always. Its been a whole week and they couldn't fix my internet or they simply couldn't care less.

Did you try changing your DNS server?

I fail to think any reason to. I can't ping any other computer on the network (internet). I usually ping (google's DNS) to test my connectivity. But as i have said i can't access the internet.