I was “assured” mobile service add on will reduce my xfinity internet service bill

I have been using xfinity since 2.5 years. I have never had an issue. Since 2 months I have contacted xfinity customer care SO many times. Its been such a hassle, waster of time and energy. 

I was “assured” by activating the mobile service my internet bill would drop to $20/month. I have saved all the screenshots of my conversation because I knew everytime they offer something and then back off. I asked them multiple times that all this hassle would be worth it in end and I had understood their promo offer well. They kept reiterating and giving full assurance.

It took them a month to send over the sim card and activate the number. After activation they asked me to contact customer service to avail the offer. After contacting them they asked may be it will be applied if I activate 2 mobile lines. Why would I keep adding on service I dont need? 

Then they suggested increasing my internet speed would increase my bill but give me $20 off. Then they were unsure of that too so asked me just to wait till system reflects the change.

why do I have to pay double the price and for mobile services that I don't even need? And why are the customer service agents so unsure about the offers and billing rates. They themselves cant understand and explain what the charges are being added. 

in the end they just asked me to wait and see what next two billing cycle would be and then figure out. Till them what am I supposed to do? Pay more for unwanted services?  

I have the screenshots of my conversations and about the offer. I am adding few of those here -