Extracting a ring tone from a noisy audio file?

Extracting a ring tone from a audio file spoiled with human made noise?

I have the following mp3 file:

How can I extract the ring tone that can be clearly heard, unfortunately mixed with the noise specific to a school yard.
I want to filter the audio file in such a way that only the ring tone remains. I have tried “Free Audio Editor” but it does not do a good job in this case. Possible, I do not know how to use it efficiently.

I think we can isolate the children, but the ring tone is hopeless.
I can’t believe you can’t find that on the internet and download a clean copy.
Anybody with a musical keyboard should be able to crank that out, too.