Rewardsco MTN outsourcing

A bunch of ******* ! I received a call from Rewardsco ( the number that they call from shows "MTN UPGRADES") and I distinctly told them that I am not interested in doing any business with them yet to my surprise they have upgraded my contract without my consent. Luckily I picked this up when checking what upgrade specials MTN have to offer but was told that I have a "Unfullfilled order". Now waiting for MTN ***** Dept to cancel this unauthorized upgrade so can I upgrade directly with MTN ! MTN how do you use a *****ulent company like Rewardsco to outsource to ?