An effective message might say: “I have a replacement fob for my vehicle, but it has never been used with it. I still have one key that starts the car. I would like to check the fob's suitability and the scope of programming.” Add the year, make, model, and city. This makes clear that the enquiry concerns an additional item rather than a key that suddenly stopped working.
For an existing remote problem, describe the actual behaviour: which buttons respond, whether the car starts, whether another key works, and when the change began. Include any recent handling or repair that might be relevant. Avoid stating that a battery, chip, or vehicle module is definitely faulty unless that has already been established by a qualified assessment you can describe.
When making arrangements, ask what needs to be present and what access is required. Keep all available keys together so you can accurately explain what you have. If the car cannot be moved, disclose that before a time is discussed. If the symptoms change before the appointment, update the same conversation; the new information may affect what should be checked.
Before the conversation ends, separate any confirmed information from details still awaiting assessment. For example, the vehicle model may be known while the suitability of a purchased fob remains open. Ask what would resolve that uncertainty and whether it affects the proposed price or timing. Keeping those points clear helps you decide what to do next without treating an initial enquiry as a guarantee that a particular item will work.