Who called from 2700

I had 2 calls from this no. +2700 and when I pick up it whoever it is hangs up, anyone has any info?

I also receive calls from this number, And as soon as I pick up they drop the phone

I Mean 2700 not 2000

Same yesterday and today the 9th of dec same number called me but didnt answer this is wired with todays tech was thinking they mighty hack my phone

I am worried as I started getting the call yesterday and today too. They dont answer back but just drop