iphone 4s full network but cant make or receive calls

hi there,

i have an iphone 4s, bought second hand.... all simcards are working with full network signal ( looks like its unlocked for any network), text messages are workin fine, 3g data is working too but

I CANT MAKE AND RECEIVE CALLS!

i checked with my carrier and they said its not barred...they tryed many settings but no luck...

I would like to use it Europe.

Why text messages are working perfectly if its blacklisted?

what can i do to make it working at least in one network in europe?

(if i turn it off and switch back on for a few swconds i can make or receive a call and after that you here only 3 short beeps when you try)