I have been lied to. and not being given discount credits

Last week chat associate  sold and offer to me  , and told me i ll get discount credit. He clearly mentioned and confirmed credit is without Port-in and trade-in and i will get the credit just by activating a new line on unlimited plan ($20) a month. I do have all the chat references available where he repeatedly assured me, When I did not see the credit applied after  a week of activation of the line. I reached out the customer support again (chat), they are tellling me the promotion does not exist. After a long chat yesterday they told me the discount will be provided and i have to visit the store to get that as they are not authorized to add the adjustment which store associated can. Today when i visited the store, store associate  said they can not help with an order created by chat associates. 

Why are they lying ? this is cheating and fraud if xfinity is not providing the discount but their associates are offering it.  

Now the chat associates are getting disconnected again and again, I have explained the issue to 5 of them in last one hour and after I explain the issue they get disconnected and a different agent gets connected.