Bias refers to a partiality or preference for one thing over another, often based on preconceived notions or prejudices. All of the scenarios you have listed involve providing information or explanations to someone, but only one of them involves a potential bias.
The scenario that reflects bias is scenario 1, where an employee of a cellular phone company explains to a customer why his company's service is superior. In this scenario, the employee's loyalty to their company and desire to sell the product may lead them to present information in a biased way, perhaps overemphasizing the positive aspects of the service and downplaying any negative aspects. The other scenarios do not involve any potential bias.