Find out why
Ask one open question. Cost pressure, a smaller team and a feature they never used lead to different answers. Do not start with an offer before you know the reason.
Say what changes
List what they keep, what they lose and when it takes effect. Include limits, seats, integrations and data. Surprises after a downgrade turn a neutral customer into an unhappy one.
Check the money honestly
Explain how billing works for the change: whether it applies now or at the next renewal, and how any credit or charge is handled. Use the figures from your pricing and your payment provider, and do not guess.
Offer alternatives only if they fit
If the real problem is price, mention a cheaper option that suits their use, such as fewer seats. Do not push a discount by reflex. It teaches customers to ask.
Make the change quickly
Do it when you say you will and confirm in writing. A slow downgrade feels like an obstacle, and the customer remembers it at renewal.
Record the reason
Tag the ticket with the reason and review the tags monthly. A rise in downgrades for one reason is a pricing or product signal.