B715 & CS Voice with outgoing calls work badly

Hi guys,

my B715 work perfectly with CS voice function, incoming and outgoing calls. With only one operator I have problems with outgoing call. I hear the voice of interlocutor but I don't understand what he say. Same operator with incoming calls work perfectly, I hear the voice and understand clearly what he say.

With a Huawei B525 same SIM and operator I have not problems, the outgoing and incoming calls work good.

Have anyone the same promblem and eventually the solution?

Thank you.