Note I said internet service not a subscription to a social media service. Your internet provider may decline to provide you with email, hell the may even decline you to provide with you with DNS, but they sure as well can't refuse to route your packets or accept incoming connections.
Apple and Google were within their rights to cut off access to the App store, but Amazon were in the wrong because they are an infrastructure company. At the very least they were obliged to allow Parler enough time to transfer to new providers.