The pre-renewal reminder

SUBJECT    Your Next Delivery Ships Thursday
PREVIEW    skip, change the date, or swap in one tap

Your next [product] ships Thursday, [date], for $[amount].

Running low?        Nothing to do. It's on its way.
Still have plenty?  [Skip this one]   [Ship in 2 weeks]
Using it faster
or slower?          [Change how often]
Want something
different?          [Swap]
Done with it?       [Cancel online]

Questions? Reply to this email. A person reads it.

[If an introductory price is ending, send this at least
7 days ahead, say so first, and keep the cancel link:
"Your first-order price was $[x]. From this delivery
it's $[y]."]

The failed-payment notices

1. SAME DAY
SUBJECT    Your Card Didn't Go Through
PREVIEW    your subscription is still here
Your card didn't go through for your [date] delivery,
so it's on hold. Your subscription is still here.
[Update your card]
We'll try again on [date]. If your card is fine,
you don't need to do anything.

2. BEFORE THE NEXT ATTEMPT
Same facts, shorter. The retry date, the button.

3. FINAL
SUBJECT    Your Subscription Ends On [Date]
We've tried your card [n] times. If we can't charge it
by [date], your subscription will end on that date.
[Update your card]   [Cancel instead]

SMS (only to subscribers who opted in to texts)
[Brand]: your card didn't go through for your next
delivery. Update it here: [link]. We'll retry [date].
Reply STOP to opt out.

The cancel flow

SCREEN 1   Cancel your subscription
           What's the main reason? (optional)
           ( ) I have too much
           ( ) It's too expensive
           ( ) I'm not using it
           ( ) I'm traveling or moving
           ( ) I want something different
           ( ) Something else: [       ]
           [Continue]   [Cancel my subscription now]

SCREEN 2   (only if a reason was chosen. Ask first, as Minnesota
           requires: "Would you like to see an option first?"
           If they say no, go straight to screen 3.)
           One option that fits the reason:
           too much     -> [Skip next]  [Every 8 weeks instead]
           expensive    -> [Smaller size] [Every 8 weeks]
           not using    -> [How to get the most from it] [Swap] [Pause]
           traveling    -> [Pause for 1 month] [Pause for 2 months]
           different    -> [Swap]
           Always beside it:  [No thanks, cancel my subscription]

SCREEN 3   Your subscription is canceled.
           Your last charge was [date]. Nothing more will ship.
           (A confirmation email follows, with the same facts.)

The yearly reminder

SUBJECT    Your Subscription, One Year On
PREVIEW    what you get, what you pay, and how to change it

You subscribe to [product], delivered every [n] weeks,
for $[amount] per delivery. In the last 12 months you
received [n] deliveries.

Change how often, skip, swap or pause:  [Manage]
Cancel anytime, online:                 [Cancel]

Subject lines in Title Case and preview text in lowercase are a house style, not a rule; keep whatever your brand uses. What matters is that the facts come first and the buttons do what they say.