A way or service capable of receiving (and transmitting) an incoming call to asterisk?

Question

Asterisk

Have a nice day everyone, that's the question.
there is a small task to “play around / try” no more ... so the task is so that I can call a number / service from a mobile or other phone, and using this service on my Asterisk I can receive a call (well, or write a file or something else, in general, process a call)
what are the services that will help solve my problem.
perhaps someone like sipnet or pсtel has the ability to call internal numbers (and the internal number will be my asterisk or otherwise) from the outside world?
or the second option, as I understand it, you can cut a regular 3G modem a little to receive calls.
an option to try, so the fastest \ simple \ cheap method is looking for.
Thanks in advance

Answer 1

Connect a landline number via SIP.
For example, here a Moscow number costs 99 rubles per month.

Answer 2

Multifon

Answer 3

Why pay money for experiments?
For example , here you can either take a Moscow mobile for free or call your SIP through extension numbers in many cities of Russia and countries around the world.
What you need for experiments.