Credits are one-time payments. Anyone — family members, friends — can add credits to your loved one's subscription.
You can make credit deposits here: https://parakeet.chat/credits
Monthly subscriptions are automatic recurring payments and require a payment method saved on file. You can set up a monthly subscription from your account page.
When it's time to renew, available credits are applied first. If your credits don't cover the full amount, the saved payment method will be charged for the remainder.