I don't get why it is Москвы
The preposition из is used with the genitive case.
Duolingo wants 'call' and refuses to accept 'ring'. 'Ring' is actually closer to the Russian usage - ' звонок ' means ' bell '.
In norwegian we would say "ring meg fra Moskva", but I never heard anyone say "ring" as anything other than a ring on the finger.
"To ring" is a synonym for "to call" and should be accepted
Ring me from Moscow was not accepted
It doesn't accept that dialect I suppose. Technically, it's right though. Report it.
Sorry, but 'call' is not very often used in the UK for telephoning people. Why can't Duolingo take this on board? 'Ring' is the everyday word that we almost always use.
Interesting, in Canada we would say call. I have heard ring of course its just not as common here or in the us. English is pretty regional. I would have considered it slang.