How to overcome or find a potential source of easy flooding on the phone from non-existent numbers?

Question

Telephony

Greetings!
I ran into a problem that put me in a dead end.
Incoming data: SIM card from MTS company, the number was registered 7 years ago (maybe more, not the point. The main thing is that there were no left owners).
Starting from Monday (18.01), calls began to arrive in the evening and at night.
If you have time to take - 2-3 seconds of silence and reset.
If you do not have time - 2-3-4 calls and reset.
If you call back - "this number does not exist."
Listing

[phone] - 23:14 / 18.01.2016
[phone] - 23:15 / 18.01.2016
[phone] - 23:35 / 18.01.2016
[phone] - 03:19 / 19.01.2016
[phone] - 03:19 / 19.01.2016
[phone]XXX - 06:17 / 19.01.2016 (домашний)
[phone] - 06:41 / 19.01.2016

[phone] - 23:27 / 19.01.2016
[phone] - 23:39 / 19.01.2016
[phone] - 23:39 / 19.01.2016
[phone] - 23:56 / 19.01.2016
[phone] - 23:56 / 19.01.2016
[phone] - 23:56 / 19.01.2016
[phone] - 23:56 / 19.01.2016 (http://ecotestexpress.ru/about)
[phone] - 23:56 / 19.01.2016

[phone] - 20:05 / 20.01.2016

With the number [phone]XXX there was a misunderstanding, because he got through, a man took it, he was surprised, because the number is home.
For now, some thoughts.
1) These are not collectors. No one presents anything, does not demand, is not rude ...
2) This is the ringing of a robot, voip telephony. (But why doesn't the number exist, it's usually "busy" from the other side if you call the gateway)
3) Maybe a schoolboy with minimal knowledge (the owner works as a teacher). Even the father of one of the hypothetical performers works at MTS, but it's too petty and stupid ...
At the moment, the "do not disturb" mode has been expanded, phones are blacklisted. MTS support kicked off as expected.
What are your thoughts gentlemen? Maybe I'm missing something.

Answer 1

Source not found:
Even I can arrange a big flood for you - just submit 10 ads on Avito with tempting offers - and you are guaranteed about 100 calls a day.
Moreover, your number in the Avito ad is not visible by search.
Confuses only the night time and the fact that you can not get through back.