...have to pay. Is it true? Please answer me if you are certain cause i want to be sure.

No it is not. Sony recently began offering their new premium service called Playstation Plus. It offers many things like full game trials and Playstation store discounts. Sony has not started charging players to play any games. There have been rumors that Activision and other companies may start charging players directly for using their servers to play games like Modern Warfare. This has not been confirmed and it would be completely independent of the console makers.

It is not true. If playstation was going to start charging they would make a big announcement about it. As far as anyone knows its only a rumor someone started so you are safe to play for free..... for now ;p