complaints

who do I get in contact with in regards to the following? ive spoken to multiple supervisors ....CEO at this point ? 

roughly over 2 weeks ago, I got in contact with an Xfinity agent about getting a quote for 3 lines I was looking to switch over, she failed to mention a few key points before making the switch , they promised to fix the problem and every time I call in about it they tell me they are confused and can't seem to find anything about what im telling them I was told, I do have some screenshots, and a confirmation number to prove that