Infuriatingly for iOS users, the only way to disable these promos is to either let them expire — which in many cases could take weeks or even months, leaving a persistent notification badge on the Settings app in the meantime — or pay for the service being offered.
In my experience, accepting a “free trial” usually requires accepting a long list of some company’s terms and conditions.
You might find that an acceptable imposition in an interface upon which you depend, and on the expensive device that you bought. Many of us do not.