Write a support macro with real variable slots instead of one so generic it needs rewriting every time

You are writing a reusable macro/canned response for a specific recurring support situation — it needs to be genuinely usable as-is most of the time, with a small number of clearly marked slots for agents to fill in, not a generic template so vague it requires substantial rewriting for every use.

SITUATION THIS MACRO COVERS
Customer asking to cancel their subscription mid-cycle and whether they get a prorated refund.

HOW OFTEN VARIATIONS OCCUR (what actually changes case to case)
Whether they're on monthly or annual billing changes the answer entirely (roughly 60/40 split); the exact refund dollar amount varies every time and must be a slot; the reason for canceling almost never changes the reply itself.

EXISTING MACROS TO AVOID OVERLAPPING
'General Cancellation Confirmation' exists but doesn't address proration at all — may need updating instead of a new macro.

BRAND VOICE
Straightforward, no forced positivity about someone leaving — don't oversell trying to save the subscription unless a save offer is specifically part of policy.

HOW TO BUILD THIS
Write the macro so the parts that are genuinely constant across every use (the core explanation, the policy statement, the closing) are fully written out, natural-sounding text — not placeholder-heavy in the parts that don't actually vary. Mark only the parts that genuinely differ case to case as explicit slots, matching what Whether they're on monthly or annual billing changes the answer entirely (roughly 60/40 split); the exact refund dollar amount varies every time and must be a slot; the reason for canceling almost never changes the reply itself. says actually changes — if a detail is true in 95% of cases, write it as the default text with a note on when to edit it, rather than making everyone fill in a slot for something almost never different. If the situation has a common branch (e.g., the reply differs meaningfully depending on one key fact), write both branches clearly labeled, not one macro trying to awkwardly cover both cases in vague language that technically works for either. Check 'General Cancellation Confirmation' exists but doesn't address proration at all — may need updating instead of a new macro. and flag if this new macro substantially overlaps with one that already exists, rather than creating a near-duplicate that agents will be confused about which to use.

WHAT NOT TO DO
Do not write a macro so generic it reads as obviously copy-pasted to the customer — a macro should sound like a real reply, not like a template with the seams showing. Do not add slots for details that rarely change; every slot is friction for the agent using it, so only add one where Whether they're on monthly or annual billing changes the answer entirely (roughly 60/40 split); the exact refund dollar amount varies every time and must be a slot; the reason for canceling almost never changes the reply itself. shows real, frequent variation.

OUTPUT FORMAT
1. The macro, with slots clearly marked (e.g., {{slot_name}}) and a one-line note on what goes in each and how often it needs changing.
2. If there's a common branch point, both versions clearly labeled with the deciding condition.
3. A note on overlap with 'General Cancellation Confirmation' exists but doesn't address proration at all — may need updating instead of a new macro., if any.