Package changes

I ordered my service at the end of July and it was installed this past Sunday.  When i spoke to the salesperson she said the xfinity services (TV) can used on smart TVs.  That is NOT true.  xfinity does not work with Sony TVs unless you by a ROKU stick.  Since i am not interested in purchasing a ROKU stick i wanted to reduce the number of channels and add another cable box.  When i called i was told i can not change what i had ordered.  

When i called to discuss the options and packages i included voice service (not cell).  I asked if i can cancel if it does not meet my expections.  If i did try to cancel this would i told the same thing i can not change my package again?  Has anyone else experience this type of service?