zyxel vmg3625-t50

Hi.

I just bought this DSL router, connect it and it started to work. Or at least it opened few web pages. but then I did a big mistake and upgraded the firmware to the latest from Zyxel site. And now my internet is not working. Indicator shows that it has a connection but any client can not open any web site, do ping or tracert. Tricky thing that when client try to open the web page it is redirected to Elisa operator portal. But my operator is Telia. How is it possible on default firmware? Please give my some hints how to solve this.