Check your subscriptions at https://my.roku.com/account/subscriptions . The due dates should be shown. There may not be anything due in the next two weeks. If no subscriptions are shown there, then your Roku payment method is irrelevant (there's no fee to use a Roku) and you need to deal with whomever you have the subscriptions through (e.g., Netflix, Hulu, etc).
You can change your payment method at https://my.roku.com , but I don't know what payment methods are available.
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