curl --request POST \
  --url https://api.kajabi.com/v1/purchases/{id}/cancel_subscription \
  --header 'Authorization: Bearer <token>'

{
  "data": {
    "id": "<string>",
    "attributes": {
      "amount_in_cents": 123,
      "payment_type": "<string>",
      "multipay_payments_made": 123,
      "opt_in": true,
      "raw_extra_contact_information": {},
      "currency": "<string>",
      "effective_start_at": "<string>",
      "cardholder_name": "<string>",
      "billing_address_zip": "<string>",
      "deactivated_at": "<string>",
      "deactivation_reason": "<string>",
      "coupon_code": "<string>",
      "source": "<string>",
      "referrer": "<string>",
      "quantity": 123,
      "created_at": "2023-11-07T05:31:56Z",
      "updated_at": "2023-11-07T05:31:56Z"
    },
    "relationships": {
      "offer": {
        "data": {
          "id": "<string>",
          "type": "<string>"
        }
      },
      "customer": {
        "data": {
          "id": "<string>",
          "type": "<string>"
        }
      },
      "transactions": {
        "data": [
          {
            "id": "<string>",
            "type": "<string>"
          }
        ]
      },
      "products": {
        "data": [
          {
            "id": "<string>",
            "type": "<string>"
          }
        ]
      }
    }
  },
  "links": {
    "self": "<string>",
    "current": "<string>"
  }
}