Free promotion never applied

I got an internet plan with Xfinity one year ago. At that time, they had a promotion for a mobile line at 0$/month for one year. Because of that, I transferred my mobile phone number. When doing that, the eSIM had issues during activation, and I asked for support from an Xfinity assistant. It took me like 7 hours, contacting different assistants through the app and calls, until one of them finally solved it. However, during the process, they activated my line 3 times (charging 3 activations, which I requested refunds for). Now, I realized they have been charging me for all the first 12 months 40$ monthly for the mobile plan. After calling them (again spending the whole morning on the phone), they told me that they charged the $40/month from the beginning cause the line was activated three times, recognizing they never applied the promotion (even when it was their error). However, they do not offer any solution/credit/reimbursement. I feel so disappointed with the service I have received from this company. Completely unrecommended for mobile plans. Hours chatting with agents/AI that do not provide any solutions, and then I have to be responsible for their mistakes...