I called back the missed call and a machine answered as "Skycall" with the option of being put on the do not call register, which I did, and now I am doubtful: Who of those criminal scammers would actually offer you to be put on a do not call register? And is it really skycall? The world has been taken over by criminals, and nothing can be believed... - anyway: It was definitely a nuisance call.

Some marketing company. Probably a scam.