"Call from nowhere" or mystic Korean phones

I found out this morning, whether a chip, or a glitch of a phone, the phone rang with the help of a blocked SIM card. Phone FlyDS500 (dual sim)

Background :
Last night, I inserted a megaphone SIM card from another phone, tried the application that works through the Internet, that is, I needed gprs. I set up a profile all the cases, I tried the application.
Simka megaphone inserted back into another phone, and blocked Tele2 in Fly when the phone is on.

History :
This morning I went to an ATM to withdraw money. Upon arrival, I found an SMS with a text about withdrawing money at an ATM, a common thing with the Sberbank card service “Mobile Bank” connected, but the SMS came to Fly, although MegaFon's SIM was plugged into another phone (hereafter iPhone). Wow, I thought.
')
Then the tests began:
Call to SIM card number - the call is accepted by Fly (simka in iphone).
A call from iphone to another number works great.
Call from Fly to another number - it works, the call is on.
Itself did not work)) says busy.

Fun thing this Fly :)))

After a while, instead of the inscription Megaphone, only the SOS inscription appeared - IMHO lost the cell where it was registered.

So much for the mysticism of Korean phones ...

Ps Try to do the same with your phone, ideally using a locked SIM card as a stub.