Help! My son is driving me mad. He passed his test in Novemeber and we have ben looking for a car ever since. He is very specific about his requirements!! ( did you know 4 doors were for OAP's

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Anyway, we have located just the thing on autotrader, it's shown as 4 miles away from us (so close yet so far) the mobile phone number given says the phone can't accept my call. I have tried texting, phoning autotrader who were as much use as...... they have the same number. He has just reduced it by £500 (obviously as he is not getting a response!)
Is there any operator service that could send him an alert or any way that I can contact him. I'm really frustrated because if this could be bought then I would be able to stop surfing car websites and would be able to spend Sundays at home rather than scouring garages.
Any suggestions greatfully received.