Yes, Amazon prime offers six months of Disney Plus free of cost through an Amazon Music Unlimited subscription. If you are new to the membership of Amazon Prime and can avail of Amazon Music Unlimited, you can receive Disney Plus for free for up to 6 months span.
If you have subscribed to Disney Plus previously, it will be free for three months. Before the promotion of Disney Plus ends, you can call off your subscription at any time. If you want to continue with Disney Plus and Amazon Music Unlimited, you will have to pay the full cost for each service.