Nowadays, there is more and more pressure on customers from vendors and service providers. Vendors and service providers try to affect customer's consumption by using different unfair practices. We can see mobile network operators using those unfair practices and therefore we focus on specific demonstrations of unethical behavior applied by mobile network operators on their customers in this thesis. We focus on it in the marketing survey as well. The diploma thesis is divided into the theoretical part and practical part. Theoretical part defines the essence of the topic from the side of marketing mix and ethics. In the practical part, we can find information about Slovak mobile network operators, who are our objects of marketing survey, and their approach to the ethics. The basis of the practical part is a marketing survey (questionnaire) aimed at specifying unethical practices applied by mobile network operators on their customers, and its evaluation. There are simple mathematical-statistical methods used for the evaluation. Based on the results of the survey, conclusions and recommendations are drawn for customers to know how to avoid these practices or to know how to proceed when they come in contact with them.