Why won't my Galaxy S6 acknowledge certain calls?

[AC Question]

My Galaxy S6 will not ring for 3 particular numbers; I do not have these numbers blocked. These people will get a message saying it's a nonworking number. I can receive texts from these people, however! I can call them, but they cannot call me.

 

[the tall guy]

Hi, have you tried speaking to your network provider encase they have blocked the callers?