Who called from 206300293

The above number keeps calling my mobile but leaves no message. I can not ring back.

They have just called me today I didn't answer

Rang me twice on my mobile within seconds. First time I declined it, second time I answered.  They asked for me /by name/ so I replied 'Who's calling?' without acknowledging. After my asking three times they hung up.

It comes up as +20 6300 293 and the originating location (from the code) says Alexandria.