I tell them I don't understand computers very well, my son used to help me with them, my eye sight isn't what it used to be, etc.
Pretty soon they'll start getting excited, convinced they've got a winner on the line.
And you finish the call with “My computer is at my son’s house and he lives in Pakistan. Isn’t India a province of Pakistan?”.
[[If I’m not busy with something I enjoy seeing how long I can keep them on the phone.]]
see my previous post for a fantastic way to keep them on the line (IF you can keep a straight face doing it lol)
I do the same. It is a challenge to see how long I can keep them tied up.