Youtube survey scam. Anyone been scammed? How does it work?

My sister tried to go to youtube.com but was instead directed to a survey. she filled it out and after, it asked for her zipcode, email, and cell phone #. She was told a pin would be sent to her phone and that she would have to enter the pin on the website. She got suspicious and she didn't actually enter the pin. I researched and found out that her phone bill could rise? would it still rise if she did not actually enter the pin? After refusing to enter the pin, she got two more txts telling her to hurry before the pin expires but has not received anything else. Should she call her cell phone provider or is she okay since she didn't go any further?