Agents can lie to customers without consequence

I contacted Xfinity customer service in regard to pushing back my bill payment. The agent deferred my payment to the next bill due date without telling me that deferring it meant I'd owe 2 bills at once. If I couldn't afford the first bill, how can I afford the second? Needless to say, the same agent insisted on being pushy and upselling me to add a new line. I was told I'd be awarded $200 in credits (not told it would only apply to that specific line). Now because I had a different phone previously connected to Xfinity service, I didn't have to physically have the phone for the agent to get me signed up. I told the agent I did not want to add the line because there was a $25 activation fee. I was then told by the agent that I could contact them within a few days, and they would be able to adjust the activation fee to $10. It did not end up coming to this because a few days after adding this line I realized I cannot physically find the phone the agent added and therefore decided to cancel the line. Upon doing so I specifically asked the agent I was chatting with if I would still be charged the activation fee. I was put on a brief hold while the agent claimed to look into this. I was told that in fact I would not be charged the activation fee, nor will I be charged a cancellation fee. I was relieved and proceeded with the cancellation. The line basically paid for itself, so this was the only charge I was worried about. A day or two later I was emailed a bill which had the activation fee still attached. I immediately contacted customer service and was told that my account had reached the maximum number of credits and that the activation would in fact not be removed. I was told to contact them again in 5-7 business days for an account credit. I did not feel the need to do this because the previous agent I spoke to claimed to have looked into the issue and assured me BEFORE I confirmed cancellation of the line. As I stated because the line paid for itself in credits, this would have been the only charge. Therefore, if it could not have been waived, I could have still chosen to keep the line with a different phone. I then asked to be escalated to a supervisor and again explained the situation. I was once again told that the activation fee was "valid" regardless of the fact that I canceled within 7 days (which apparently is some kind of policy). After not receiving any solution to the fact that an Xfinity agent lied to me, I called customer service. I was again told by another agent that there was nothing that could be done, period. I asked to speak to a supervisor and was told a supervisor was not available and I would receive a call back. The next morning, I contacted their customer service chat and asked for an email or way to file a formal complaint. The first agent claimed to escalate me. Upon transfer the next chat agent abruptly ended the chat without warning. I recontacted the chat agent who provided me with a new number in which to speak to someone in regard to my issue instead of obliging my request to provide me with a way or instructions on how to make a formal complaint. Their practices seem unpolished and unprofessional at best.