Doesn't "απόδειξη " mean "proof" ? when I answered "I want a proof", the answer was wrongs and the correct answer was "I want a receipt"?
And why is it pronounced apotexee ? why the delta sounds as T?
A receipt is proof of purchase ;)
And you're right, the audio is wrong. The word is not pronounced with a t, but with a th like in "that". Check the (better) audio here (it's not perfect as it starts with a ha rather than an a, but the rest is clear), or use this tool which is usually very good and can be used for whole phrases. Forvo is another option too.
I think "I want proof" is strange... I suppose a native speaker would say "I want a proof"...
The word "proof" is considered to be uncountable in English. It could be considered countable in cases lke printing or mathematics, or physics, but still, it's mostly used in it's uncountable form ^.^