The verb call has multiple meanings in English.
It may be used for calling someone on their phone (therefore, καλώ, τηλεφωνώ, or παίρνω τηλέφωνο in Greek.)
It may be used to name, identify or describe sne or sth (in which case, ονομάζω, and αποκαλώ would be used in Greek.)
It could also be used to summon, request of beckon (in which case, καλώ would be used.)
It depends on the meaning and context. ^.^
Thanks. Your link does indeed sound like καλούν to me.
Here's καλήν from the same site: https://es.forvo.com/search/%CE%BA%CE%B1%CE%BB%CE%AE%CE%BD/
But Duo's TTS here still sounds much more like Forvo's καλήν than καλούν to me!
The question tone is not reproduced here. I know I should be looking at the punctuation, but the tone is entrapment. Of course, I have the opposite problem in some other programmes tgat always seem to be in the question tone. Perhaps we should leave the tone to the Chinese and Vietnamese programmes.
It's a whole different symbol, so that makes sense, but it's not like exercises are deemed incorrect whenever punctuation is the only omission. It doesn't sound like a clear question, but this doesn't affect the correct answer (even when it's a "type-what-you-hear" exercise, one can't get it wrong if they type in the words they hear).
Every punctuation symbol is different in every language, or we would simply call the ones that were the same one symbol. I did speak too rashly, though, as only some of the languages that do not change the structure of the sentence when making a question accept the answer as a statement as correct.